flowers and insects: xxv

Flowers and Insects: XXVAuthor(s): Charles RobertsonReviewed work(s):Source: Ecology, Vol. 9, No. 4 (Oct., 1928), pp. 505-526Published by: Ecological Society of AmericaStable URL: http://www.jstor.org/stable/1929418 .Accessed: 25/08/2012 18:31

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FLOWERS AND INSECTS. XXV

CHARLES ROBERTSON

Carlinville, Illinois

"Floweros aiid Insect" Papers.-To make them accessible, these papers were published as nearly as possible in the same place, I-XXIII in the Botanical Gazette, I4, 1889 to 78, 1924, the overflow; " Umbelliferae," "Asclepiadaceae to Scrophulariaceae," " Labiatae," " Rosaceae and Com- positae," " Contributions" in Trans. St. Louis Acad. Sci., 5, 6, 7, I89o I8c6,

and the " Philosophy of flower seasons" in the American Naturalist, 29,

1895, to follow Clarke's paper (I7). Some seem to hold that these were outlandish publications which they were under no obligations to cite.

Clements and Long (29) say: " No previous floral study of Rubus has been made in America, but several European species have received much attention (Knuth, 1908: 352)," and " The pollination of the rose appears to have received no attention in this country, but several species have been studied in Europe (Knuth T906: 348)." The Davis translation excludes all American observations. Knut-h (1904, III, I, 340, 344) gives abstracts of Rublus occidentalis and villosus, Rosa hurnilis and setigera, and cites my " Rosaceae and Compositae " of i894. These are also mentioned in the Botanisches Ccntralblatt and in Juist's Botanischer Jahresbericht. Abstracts of llertensia vir-ginica, Castilleja coccinea, Pentstenm on laevigatus and pubescens in " Asclepiadaceae to Scrophulariaceae," i89i, and Monarda bradburiacua and fistulosa in " Labiatae," i890, are contained in the same publications, along with abstracts of the " Flowers and insects " papers, I-XIX. Those of Knuth's " Handbuch der Bltitenbiologie" are in his Band III, Teil I, 1904 and Teil 2, 1905. The first paper ever published on visits of oligotropic bees (" Flowers and insects XIX," i899), and ignored by authors, was abstracted in the above three places and in the Illustrierte Zeitschrift fuir Entomologie, 5: 307-II, I900.

Mixing Heterogeneous Data.-Huxley referred to the superstition mani- fested by those who mix heterogeneous data just as if they should throw all sorts of grains into a hopper and expect to grind out wheat flour. When those who affect scientific authority mix such data, it is not surprising that science is mixed with art and technology, as " theoretical " and " applied.'

In 25 and 26 criticism was made regarding the mixing of anthecological (lata with collector's notes. A better illustration is in the case of 27 Com- positae (Knuth 21) whose visitors were observed by Mueller and Alfken.

505

506 CHARLES ROBERTSON Ecology, Vol. IX, No. 4

Bees Flies Other Hym. Lep. Other Visitors Total

Mueller ............. 388 252 84 io8 90 922 Alfken .326 62 24 1 7 4 433

According to Mueller's lists, bees make 42 per cent of the visits, while according, to Alfken's lists bees make 75.2. Of the total bee visits, Mueller's lists show 54.3 per cent and Alfken's show 45.6. Of the total visits of other insects, Mueller's lists show 83.3 per cent (5 times as many) and Alfken's i6.6. Mueller found other insects in all except i case, while Alfken found them in only 14 cases. The conclusion is that Alfken's data were selected and do not belong in the work.

Flower Colors and Insect Visits.-Sprengel (I, 29) distinguished wind flowers and insect flowers and held that the general colors of the latter served " to attract the notice of insects while still at a distance and that special colors of parts of the flowers, pathfinders or nectar-guides, served to guide the insect to the nectar after it had settled on the flower." He pointed out that entomophilous flowers were sometimes zygomorphous while anemophilous were not. The fact that insects in search of pollen readily find anemophilous flowers does not prove that the colors of entomophilous flowers are of no advantage in facilitating their visits. It seems to me that generally statements which oppose Sprengel's views are erroneous and those which support them are second-hand. Just so, arguments for evolution are no longer contributions to science, but are only instructions to the ignorant. It is the business of anthecology to explain the differences between wind and insect flowers, not to deny their significance.

Those who ignore Sprengel's conclusions should explain the following:

i. The presence of colors in entomophilous flowers and their absence in anemophilous ones.

2. The presence of zygomorphy in entomophilous flowers and its absence in anemophilous ones.

3. The presence of pathfinders in complicated flowers and their absence in many simple ones, as well as in night flowers.

4. The presence of pathfinders in the new flowers of Lantana and absence in old ones.

5. The general association of red colors with deep-seated nectar and of white with shallow nectar.

6. Some flowers surrounded by colored bracts are inconspicuous, Corn us, Araceae and Castilleia. Exposed flowers of Cornus and Araceae are colored. Keels of Crotalaria and Lupinus, enclosed by the wings, are not colored.

The facility with which insects find their plant food and the difficulty with which the economic entomologists, with their insecticides, keep them

October, I928 FLOWERS AND INSECTS 507

away from it, show that flower colors exist as extra facilities in enabling them to find and return to flowers.1

Visits of insects are almost invariably determined by the food which the flowers supply, though they are facilitated by the colors. Anemophilous flowers are visited by pollen-eating insects and by bees which can collect the pollen by mixing it with honey. Pollen flowers are visited by female bees, syrphids and beetles. Ordinary flowers are visited by miscellaneous insects for nectar and pollen. The only visits determined by the colors are explora- tory, like those of nectar seeking insects to pollen flowers.

A follower of Lutz states that it has been proved that insects were color- blind 2 except to ultraviolet and that their visits to flowers were determined by these reflections.

Among, the curiosities of literature, the subject of insect visitors and flower colors has formed a stamping ground for "argufiers" hardly equaled by the discussions of free will and necessity. The proposition that insects visit flowers for nectar and pollen, that but for these substances their visits

would be rare and that the forms and colors of flowers facilitate their visits, hardly leaves much opening for endless " argufying " as to wvhy insects visit

flowers. The fact that bees visit flowers was recorded in the Iliad and that

in about the most obvious thing that they do. The experimental augurs assume that there is something quite mysterious

about the visits of bees to colored flowers, ignoring the fact that these insects visit anemophilous flowers which are quite greenish. They assume that it is very important to observe whether bees react to certain colors; that these

1 The anthropocentric philosophers would be glad to show that insects are color

blind and that flower colors were made to please man. Those who argue f rom the

testimony of majorities might readily conclude that they had solved the problem. The opponents of the theory of natural selection reject that theory as a cause for

adaptation, and fall back upon Paley. In a recent article we read: " A rose, a violet, a

sunset, a thrush's song, seem rather the expression of a beauty-loving, benevolent, pleas-

ure-providing Creator, designing not merely necessities but something over and above,

adapted to give the purest and most delicately refined joys and pleasures for the promo-

tion of graces of character in his noblest creatures." "All of these difficulties are re-

moved by the conception of the creating and guiding activity of God." These " noblest

creatures " don't see more than a smear of color. What the anthecologist wants is to

see what he can account for as a consequence of natural laws. He does not care to

substitute " comfortable doctrines" for an intellectual life, or to take the easiest way and

wait until he gets "up yonder." One man says: " What does your science all amount

to? When I get up yonder, I will know all about these things." The application of the above quoted proposition by the greatest of the spiritualistic

teleologists led to discrepancies which required the introduction of Satan and sin. The

plan miscarried in this world but it will be better next time. In general applications

of the proposition lead to such unsatisfactory conclusions as that the world was made

for fish and that man's hair was made to shelter pediculi. 2 Accounting for flower colors by denying their existence as far as insects are con-

cerned reminds one of the state-educated people who would dispose of evolution by claim-

ing it never happened.


reactions will be correlated with. and throw light upon, their flower visits; that the reactions of the hive-bee, an introduced, domesticated insect which is maintained in numbers sufficient to crowd the flora, will be good for all bees. They say " bees " when they mean hive-bees. They assume that this bee retains definite qualities like inanimate substancs, and that one generation is like another; that the reactions are simple and that experience, heredity or natural selection have nothing to do with them.

DYSTROPIC COLOR PREFERENCES

If experimental color preferences are of anthecological value, they ought to harmonize with the flowers visited and the visits of insects, otherwise they are dystropic. Lubbock (8) showed that according to its reactions the hive- bee preferred blue. A preference for blue is evidently dystropic because there are not many blue flowers and because blue flowers probably show a higher percentage than any other of nectaries which these bees cannot exhaust.

Lutz (30) holds that the hive-bee definitely reacts toward ultraviolet. This is also dystropic because there are few flowers with that reflection. Of i96 flowers pollinated by the hive-bee, 43.3 per cent are white, 32.1 yellow and on11y 24.4 are red. In its original state as a wild bee, its visits may have shown a marked preponderance of blue.

A recent abstract says: " The data obtained by these methods are of the very greatest significance. Many yellow flowers are shown to reflect a considerable proportion of ultraviolet, white flowers rarely reflect much ultraviolet and many blue flowers reflect little or no ultraviolet. . . . The results

of a long series of experiments on bees, wasps, syrphid flies, and other flower- visiting insects, showed that in every case in which an insect reacted to any illumination it reacted definitely to ultraviolet."

The " very greatest significance " of these data seems to be that it leaves one guessing about what flowers are ultraviolet and what that has to do, anyhow, with the visits of insects. It looks as if ultraviolet flowers were not numerous and their reflections unimportant.

Bees.-Of 437 local flowers whose visitors were observed, 39.I per cent

are white, 30.6 yellow and 30.2 red. Of 417 flowers pollinated by bees, 40.0

per cent are white, 31.1 yellow and 28.7 red. Of 6063 pollinating bee visits to these flowers, 43.2 per cent are to white, 33.5 to yellow and 23.1 to red. A preference for ultraviolet appears to be dystropic.

Wasps.-Of i82 flowers pollinated by wasps, 50.5 per cent are white 32.7 yellow and T6.6 red. Of 2,iii pollinating visits to these flowers, 63.5

per cent are to white, 28.o to yellow and 8.3 to red. If white flowers rarely reflect much ultraviolet, wasps visit them anyhow, and a preference for that reflection seems to be dystropic.

Syrphlidae.-Of 203 flowers pollinated by Syrphidae, 5I.7 per cent are white, 33.0 yellow and 15.2 are red. Of i,i65 pollinating visits to these

October, 1(28 FLOWERS AND INSE1CTS 509

flowers, 58.8 per cent are to white, 33.9 to yellow and 7.2 to red. If they

prefer an ultraviolet filter, it does not follow that they will leave the accessible

pollen and nectar of a white flower to sit on a closed flower reflecting ultra-

violet. Of go Syrphidae, Rhzingi(a fasica is the only one having a decided

preference for red. It shows 43.7 under red and 43.7 under white. This

syrphid has the longest tongue of anv of the go species, which explains its

visits to flowers that are largely red. In 56 visits Eristalis diinidiatus shows

57.1 per cent under white and 3 3.9 ullder yellow. In 50 visits E. transsversus

shows 25 un(ler yellow and 21 under white. The Syrphidae visit for pollen many large flowers whose nectar they

cannot reach and whose stigomas they do not touch. Of 145 non-pollinating visits, 42.7 per cent are to red and only 9.6 to white.

The association of female bees, syrphids and beetles on such flowers as

roses, does not prove a preference for the colors, but results from the fact

that the flowers contain pollen and no nectar. Unless it can be shown that

white flowers commonly reflect ultraviolet any preference of bees, wasps and

syrphids for that reflection must be regarded as dystropic. Preference of

these insects for ultraviolet is about as important as the habit of moths of

abandoning their ordinary behavior to batter themselves against a light. The

case of ultraviolet reminds me of the case of the mountain which gave birth to

a mouse.

FLOWER VISITING HABITS HEREDITARY

I have stated (20) that " the relations of host-bees to the flowers from

which they get pollen are quite analogous to the relations of parasites to their

hosts, of phytophagous insects to their foods plants, or of predaceous insects

to the insects upon which they feed or with which they provision their nests."

That is, they are largely hereditary. Oligolcetic Bees.-In 34, 428, it was pointed out that 28.3 per cent of

local l)ees are oligolectic. They collect pollen of certain related flowers.

One claims that the color attracts the visitor, another that it is the odor.

I have observed Physalis lanceolata and Hezucliera hispida growing together,

both having pollen, nectar, color and odor, the former visited for pollen by

Collctes latitarsis, the latter by C. aestivalis. As simple reactions there is

no reason why the bees should not visit both species for pollen.

Polylectic Bees.-In their pollen visits to (Conpositae, the Halictidae

females show a heterotropy which seems to depend upon heredity. The

pollen is exposed and the flight of the bees is synchronous. Some percentages

are: C111oralictus zephyrus 5.0, sparsus 22.2, pilosus 34.3, coreopsis 75.0;

Evylaeus f oxii 6.6, pectorahs 31 .1 ; Oxystoglossa conf usa i i.6, Halictus lerouxii 12.8, Seladonia fasciata 17.6, Augochlora viridula 27.2, Odontalictius ligatus 69.i; Agapostemton radiatus 20.0, virescens 38.7, texanus 83.3.

Pollen visits to Compositae are for Calliopsis andrenifo-rmnis i0.3, while

for Neotrypetes carinatus, flying at the same time, they are 74.0. Melissodes

510 CHARLES ROBERTSON Ecology, Vol. IX, No.4A

bimuaculata shows i6.6. Epimtelissodes obliqeta, flying at the same time, shows 89.2.

An important condition of natural selection is different reactions under the same conditions. And that is exactly what species do.

Of their l)ollen visits, the bumblebee workers show the following percentages to Compositae: Bowl bus birnaculatus o.o, Bomnbias separates 5.2,

auriconiis o10., zagans 21.4, 2 aicricanoru?1 23.6, impatiens 39.2, Bombias scuteilaris 42.8.

Visits to Compositae of male bumblebees of 7 species ranged from i6.6 per cent for Boilbus bimaculatus to 92.3 for Bonlbias scutcllaris, and visits of male Halictidae of i8 species ranged from 9.3 per cent for Halictus lerouxii to 72.2 for Odontalictus ligatus (34).

In their l)ollen visits to Rosaceae 6 species of Andrena show the following diversity: A. carlini i6.6 per cent, nasonui 20.0, mandibularis 28.5, sayi 40.0, pruni 50.0, dunningii 75.0.

Hereditary Habits of Introduced Bees.-Thompson (i5) has given a list

of flowers visited by Bombi introduced in New Zealand, and states that, with a few exceptions, he has never heard of these bees visiting the flowers of indligenous plants.

I suspect that Anthernois centuncularis is introduced from Europe, because, while I have taken it on io different flowers, I could not get all the specimens I wanted except on Asparagus officials which is escaped from

cultivation, and which is one of 20 flowers visited by the bee in Europe. Hawk Moths.-The case mentioned in 32, 79, of a hawk-moth visiting

the white petunias and avoiding the purple ones was supposed to have something to do with the white colors of night flowers. I find only two local indigenous sphingophilous flowers, Hab enaria leucophaea with white flowers and Argave virginica with greenish yellow flowers. It is certain that hawk- moths are not going to get enough nectar from white flowers. Of their visits, 95.4 per cent are to flowers with deep-seated nectar, Ma and Mas, 52.3 per cent of which are red and 17.7 per cent white. The visits show 63.8 per cent under red and 31.8 under white. Of the visits to white flowers, i8.i per cent are to introduced species of Datura.

Adaptations of Flowers and Insects Associated zith the Colors We See.- In general, red flowers have the deepest tubes, yellow flowers have intermediate tubes, while white flowers have the shortest. In the case of 437 flowers and 13,971 visits, as we pass from red flowers through yellow to white, the average visits are 17.8, 33.2 and 4I.8 per cent. The visits of the following increase: short-tongued bees 433, 1,183 and 1,828, flies 294, 1,247 and 2,234

lower Hymenoptera 178, 700, I;482, Coleoptera and Hemiptera 35, 173, 343. The visits of long-tongued bees decline, 984, 870, 794. The other long- tongued group, Lepidoptera, does not show a regular decline, but makes I8 4 per cent of the visits to red and only 6.6 per cent of those to white. Red shows 30.2 per cent of the flowers and only i6.8 per cent of the visits. White

October, 1928 FLOWERS AND INSECTS 511

shows 39.1 per cent of the flowers and 5i.0 per cent of the visits. Yellow is

quite intermediate, with 30.6 per cent of the flowers and 31.9 per cent of the visits. Here the colors we see, the adaptations of insects to flowers and the

flower visits are correlated. In B' the long-tongued bee visits show 36.9, 30.3, 9.3 per cent, and the

Lepidoptera show 28.3, 9.6, S.i, the highest perecntages under red. The short-tongued bees show 14.1, I5.5, 21.0, flies I6.3, 24.3, 35.4, and lower

Hymenoptera 2.5, 17.0, 35.4, the highest percentages under white. Red, with deep tubes, shows 21.8 per cent of the flowers and 13.6 per cent of the visits. \Vhite, with short tubes, shows 31 per cent of the flowers and 37.4 per cent of the visits. The dominant color, yellow, with mid-length tubes, shows 47.1

per cent of the flowers and 48.8 per cent of the visits. Here also there is a correlation between the flower colors, insect tongues and insect visits. Of

the long-tongued bee flowers, 62 per cent are yellow and 36 per cent red.

Of the short-tongued bee flowers 28.5 per cent are yellow and 71.4 per cent white (32, 82).

Colors of Natural Groups.-In 99 species of Alismales, Liliales, Ranales

Parietales, Caryophyllales, Rosaceae and Saxifragaceae, 55.5 per cent are

white. Red is a specialized color occurring in i9.i per cent of the cases.

Of the long-tongued bee flowers 65.2 per cent are red. Of the short-tongue(l bee flowers 63.1 per cent are white.

Of 99 Gentianales, Personales, Lamiales and Legouminosae, 59.5 per cent

are red. The majority are long-tongued bee flowers of which 70.4 per cent

are red. White seems to be a specialized color, occurring in only 27.2 per

cent of the species. I regard Lycopus, Pycnaitheimiunt and Menthla as specialized Labiatae. Of the short-tongued bee flowers, 64.2 per cent are white.

White, whether a simple or a specialized color, usually belongs to short-tul)ed

flowers a(lapted to short-tonged bees. In the Asterales yellow is the typical color, while red is a specialized

color associated with deep tubes and white is a specialized color associated

with shallow tubes. Colors of Flower Classes.-Mueller's long-tongued bee flowers (HI), here

including butterfly and bird flowers) show 58.5 per cent red and 25.i white.

B' has 47.1 per cent yellow and 31.0 white. All of his other classes have

maxima un(ler white. The simplest flowers, those with partly concealed

nectar, AB, show 64. I per cent white and 34.3 yellow, those with exposed nectar, A, show 52.5 per cent white and 40.0 yellow, while those with con-

cealed nectar, B, have 48.7 white and 27.5 yellow. Taken together these

show 55 per cent under white and 32.6 under yellow. There is a pretty regular relation between the colors we see and the nectar concealment.

In my classes non-social flowers with deep-seated nectar, Ma, have 57.5 per cent red and 21.9 white. Non-social flowers with shallow nectaries!, Mi, show white 50 per cent, yellow 35.8. Maxima under Mli were always associ-

33


ate(d with mlaximia under white. Of the social flowers with shallow nectaries, Mis, 65.9 per cent are white and 29.7 yellow. Of 43 cases with maxima un(ler Mis, 41 showed maxima under white and 2 under yellow. Of the

l)olytro)ic flowers, Pol, 78.2 per cent are white and 17.3 yellow. Maxima tinder Pol were associated with maxima under white in 91.6 per cent of the cases.

Visits of Oligoleges to Unrelated Flowers.-It is a common thing to hear people cover their ignorance by prating about " culture." So persons who have made few observations use high-sounding phrases like "observed conditions."

In I899 (20) it was shown that the restriction is not in nectar sucking but in pollen collecting, in which the tongue is rarely used. Ignoring this and imagining that tongue-length limits a bee to a few flowers, and that only a few flowers are synchronous, some authors suppose that they have ex-

plained what they call " oligotropism," meaning- exclusiveness, by "tongue- length " and " svnichronism." Some, olig-oleges belong to l)ollen flowers and some to flowers whose nectar they can hardly reach. If bees visited for pollen all the synchronous flowers whose nectar they could reach, there would be no oligolectic bees. For every oligolege there can be found a )olylege with the same tongtue-length and flying throughout the same period.

Of 7I oligoleges of which both sexes are known, the females average 54.5 days and the males 39.1 (24). Besides getting nectar for themselves the females mix the pollen with honev and so might be expected to extend their range for the nectar of flowers unrelated to those from which they get pollen. Macro p is steiron e oiratis, Epimtelissodes stripes and Anmegilla walshii,

oligoleges of pollen flowers, get all of their nectar from unrelated flowers. Of the visits of the females of the 7i species, 28.1 per cent are nectar visits to unrelated flowers. The males have shorter tongues, flight shorter by 1 5.4 days, and probably similar hereditary predilections for the same flowers. They have to get only enough nectar for themselves and so might be expected to satisfy themselves with the nectar of the favorite flowers. Of their visits, however, 42.1 per cent are to unrelated flowers. This is another example of what " tongue-length," " short flight " and " synchronism "

amount to. It has been pointed out (20) that from the standpoint of natural

selection, it is an advantage for the males to extend their nectar visits and not

compete with the females in their more important work. Constancy of Bee Visits.-Mvlueller (4) who made more observations oln

flower visits than any other European, says that in general anthophilous insects wander about getting their food on whatever flowers they find it. The observations are so easy to make and the results so obvious that the first statements may be taken as correct and the rest as second-hand. Accordingly I)arwin's, lately garbeled, account (5, 415) will about suffice: " All kinds of bees and certain other insects usually visit the flowers of the same species as

October, 1928 FLOWERS AND INSECTS 5I3

long as they can, before going to other species. This fact was observed by Aristotle with respect to the hive-bee more than 2,000 years ago, and was noticed by Dobbs in 1736 in the Philosophical Transactions. It may be observed by any one, both with hive and humble-bees in every flower garden: not that the habit is invariably followed." The last statement has been veri- fied by almost everyone who has spent a day or two in the field. The majority have seen bees change from one species to another. In my second paper (9) I mentioned two colors of pollen in baskets of Bombias scutellaris. What I observe once I assume occurs frequently. One observation like this is as good as i,ooo and does not take up as many pages. It is not clear why an elaborate system is adopted to verify what every observer has seen in the first few davs.

Of the flowers visited by a given bee, some are common, grow in large latches and furnish an abundance of nectar and pollen, while others are rare, scattered and furnish little food. It is obvious that bees should show a varying degree of constancy under these conditions. I have observed Odontalictus ligatus visiting i27 species of flowers. On Helianthus annuus it was io.9

per cent of 467 individuals and obviously quite constant. One would not expect it to spend so much time on Scutellaria parvula or Stellaria media. On one day where there are a variety of flowers it is easy to observe bees change from one species to another, and that while standing in one place. The question would hardly be started by one who was aware of the varying degree of frequency of indigenous flowers.

Non-pollinating Visits.-I have seen 77 species of bees make 262 visits to flowers whose nectar they could not reach in the legitimate way. This shows that there are not enough flowers for bees to limit themselves to the most favorable.

Nature's Garden.-The most interesting thing in anthecology is the observation of the living plants and insects in the field. Sitting in a comfortable chair and examining bees long dead is a miserable substitute. The chair business is illustrated by the practices of Huxley's " species makers, the hodmen of science," who describe the sexes of bees as different species. No competent collector would do much of that. It would be a compliment to call one of these species-mongers a " hodman," for a hodman would not break his bricks in two.

PROBABILITY OF POLLEN SHOWING WHERE A BEE HAS BEEN

Loose Pollen and Asclepiad Pollinia.-In i887 (9) I discussed the advantage of pollinia over loose pollen. Female bees wipe off the loose pollen and place it in their scopae, so that they will show the pollen of only one trip. On Triosteumn perfoliatum, Bomibus vagans, and, on Dodecatheon meadia, Bomnbus americanorum wiped the pollen from their faces and tongues simply to get rid of it. But bumblebees tried in vain to wipe off the pollinia


of Acerates lon gifolia. I saw a female of Boinbus ainericanorurn try to pull off pollinia of Orchlis spectabilis. Bees wipinfg off the pollen throw doubt on

the affected accuracy of examining them for pollen. Occurrence of Pollen on Visitors.-When an insect sucks nectar in the

normal way and might be expected to effect pollination, I have counted it as

doing so, but I have often wondered if a considerable percentage would not

fail to show any pollen, especially when they were visiting flowers which had been open for some time.

Visits to Asclepiads.-Of visits to Asclepiads and Apocynumn, 273 showed

pollinia and 308 did not. Bee visits were 21.6 per cent of the former and 32.1 of the latter. Scolia bicincta, taken on Asclepias verticillata (9, 249),

had pollinia of this and of A. syriaca. A Papilio, taken on A. syriaca, had

only pollinia of A. tuberosa. At Inverness, Florida, of 45 bees taken on

Asclepias amplexicaulis, only 5 carried pollinia, while of 68 bees taken on

Arnsonia ciliatc, only i9 showed pollen on their tongues. By identifying the

pollinia, I have added to my lists of visitors to 6 local species of Asclepias I I1 insects which were captured on other flowers.

Diclinous Flowers.-On 8 species I observed 54 bee visits to the pistillate

flowers only. Of the 437 local flowers on which I have taken insects, 26 are

diclinous. Visitors to the pistillate flowers would show no pollen.

Gynopleogarnous Flowers.-These have pistillate forms. Here Knuth

(I9, 36) gives: " Hepatica, Ranunculus-Arten, die meisten deutschen Di-

antheen, manche Lychnideen, fast sdmptliche Alsineen, viele Arten von

Geranium, Potentilla, Epilobium, ferner Ribes Grossularia, Saxifraga op-

positifolia, Sherardia arvensis, (lie meisten Dipsacacceen, Convolvulus,

Anchusa, Echium, Verbascum und Digitalis-Arten, die meisten deutschen

Labiaten, Plantago-Arten, Polygonum amphibium u. a." Visits to the pis-

tillate flowers would show no pollen. Gynodiecious and Eripleogantolis Plants.-These have pistillate flowers,

visits to which would also show no pollen trace. Dicho gany.-Proterogynous flowers admit insects before the pollen is

discharged. In proterandrous flowers the anthers are often empty or turned

out of the line of contact before the stigmas are receptive. A considerable

number of visits are likely to show no pollen. Bees Not Touching Anthers.-I have seen bees getting nectar without

touching anthers of Agastache nepetoides, Cypripediu in pubescens, Geranium

maculaturn, Gerardia tenuifoelat, Lobelia cardinalis. L. siphilitica, Melanthi1 in

virginicum, Mertensia. virginica, Monarda bradburiana, Polygonaturn coin-

mutatumn, Ribes gracile, Scutellaria canescens, Teucrimn n canadense, Triosteumn

perfoliatut. Viola cucullata, V. pubescens, V. strata. Usually this is a

case of small bees and large flowers. Perforated Flowers.-Sprengel (i) saw bees perforating and using the

holes in several flowers. Pammel (io) gives a list of I40 perforated flowers

and 136 titles most of which relate to perforation. I have observed 13 visits

October, I928 FLOWERS AND INSECTS 5I5

of bees to holes made by Leionotus foraminatus and L. dorsalis in flowers of Moniarda bradburiatno, M. fistulosa and Scuttellaria canescens. Mueller (4) observed 20 visits of bees to holes in 17 flowers which had been perforated by Bomnbus terrcster. In the Tyrol, Schulz (13) found 125 species perforated by the same bumblebee. The bees making the holes and those using them are not likely to show pollen.

Getting Nectar front Unopened Flowers and front the Outside.-Ogle (3) saw bumblebees forcing their tongues into flower-buds of Pedicularis sylvatica. MA/any similar cases have been recorded. On German rivale, Mueller (4) saw Born bus tcrrester sucking nectar from unopened flowers. On open ones he saw this and other bumniblebees obtaining nectar from the outside without touching the anthers.

Inqiiiline and Male Bees.-These are less hairy and less likely to show pollen than the nest-making and female bees.

Homnogarnous Flowers.-If the bees visiting ordinary flowers from the time the first one opens until the last one closes are captured and examined, I should not be surprised if io per cent failed to show any pollen.

Conclusion.-Counting diclinous, dichogamous, perforated flowers and Lobelia (7) at least i0 per cent of flowers observed by me permit bee visits without pollen trace. Altogether, it is not clear that examining bees for pollen " would be more productive of results."

Evainning Bees for Poll.'ui.-In 1887 (9) I have recorded a case of Bombbias scutellaris which had in its baskets pollen of Petalostemiunt pur- piureum, on which it was caught, and dark pollen from another flower; and besides carried pollinia of Acerates floridana and viridiflora. I have often resorted to examination to make sure that the pollen came from the flowers on which the bees were taken, and that is the most that it is good for. The first specimen of Ptilandrena g. mnaculati I ever saw was sucking on Heracleunt lanatuim and had her scopae full of large pollen grains, which proved to be from Geranium inaculatum. On Lithospermnun canescens I found 3 species of Osmia whose scopae held pollen of Hypoxis hirsute. I added to the list in this way, but Lithospermumi canescens is a poor place to look for visitors of Hypoxis hirsuta. This is a pollen flower and the bees probably went to the Lithospermumi for nectar to mix with the pollen at the nests.

Determtining Species by Pollen.-Tschernich (ii) refers to characteristic pollen in species of the same genus as if its occurrence were rather excep- tional. In considering this matter a long time ago, I decided that related species could not be identified by the pollen. A bee referred for identifica- tion of pollen was said to have pollen from "Mertensia sp.," indicating that the species could not be determined.

Easy Chair Work.-I have seen Bombus amtericanorum visit 236 local flowers. How long would it take and how many specimens would it take

5i6 CHARLES ROBERTSON Ecology, Vol. IX, No. 4

to show pollen from 236 flowers? There would be no way to do this without collecting the specimens throughout the season, and in so many localities that it would be better to observe the visitors of different flowers and then make out the visits. There would be little probability of specimens showing that many kinds of pollen unless they were taken on 236 different flowers. I doubt if all of the specimens in all of the collections would show as many. At Inverness, Florida, on Laurocerasus caroliniana, I captured 527 specimens of Opandrena scutellaris. What likelihood of these showing much pollen of other flowers? Each bee has to be captured separately with a clean bottle and a clean net so as not to get the pollen from the other bees.

Flower Visits of Bees.-In anthecology the essential thing is to make out lists of the insect visitors to flowers. If it is desirable to make out lists of the flower visits of the insects, these may be compiled from the lists of visitors. To make an elaborate system to determine the question (second- hand since i884) whether bees, as if they were all alike, are constant seems hardly worth while. To make out the flower visits of bees, examination of specimens for pollen is unreliable because they do not always show pollen, and it is impossible always to distinguish pollen which was being collected from that which was incidental to nectar visits. This is an entomological subject which little concerns anthecology. The following gives the total visits and the percentages of bee visits for several regions: Illinois 13.971,

43.3; Germany, Mueller 5,231, 4I.3; Flanders, MacLeod 2,032, 30.I; Florida

(Jan.-Apr.) 643, 23.6; Pyrenees, MacLeod, I,697, 25.4; Alps generally, Mueller 5,712, 20.0; Alps above tree limits, Mueller 2,779, 14.4. So that bees

make 23.6 to 43.3 per cent of the insect visits in lowlands, and I4.4 to 25.4 per cent of the insect visits in highlands. In mountain regions bees probably make only about 20 per cent of the insect visits to flowers.

POLLEN LOADS

Composition of Pollen Loads.-Under this head Clements and Long (29,

I 19) have mixed three subjects, loads of nest-making, bees which are collecting, pollen, of nest-makers which are not collecting it, and of inquilines which do not use pollen. Since the sexes were not indicated, male bees mav have been mixed with the females and workers. "Load " as used by them evidently does not distinguish between a load made by a female bee collecting pollen and the loose pollen bourne by an inquiline bee on its nectar visits. Of 207 bees listed by them I21 showed one kind of pollen, while 86 showed pollen from more than one species of flower. Of these mixed bees, they say hardly any one was " perfectly constant in its choice of pollen."

Pollen Loads and Pollen Flowers.-Of 437 entomophilous flowers, at least 7 per cent are nectarless flowers of which female nest-making bees collect the pollen. Since these bees mix the pollen with honey while collecting it, or at the nest, it is fairly inevitable that they would show some pollen from flowers which they were visiting only for nectar.


I have stumbled on the hive-bee collecting pollen from I I different anemophilous plants whose pollen it could hardly collect without mixing with honey. These pollen loads are likely to show pollen from flowers which it was visiting for nectar.

In several cases I have found some pollen from the flower on which a bee was sucking adhering to scopae filled with pollen from another flower.

Bees visiting flowers for nectar often have their whole undersides covered with pollen enough to fill their scopae without trying to locate it in their brushes. Unless they removed it, they would show a considerable mixture of this pollen when they turned to collecting pollen of another flower.

Constancy and Pollen Loads.-Clements and Long say (29, 135) "The composition of pollen loads can only reveal the behavior of bees in the col- lection of pollen." They say, however, that Prosopis varifrons has pollen showing 33.0 per cent of its body weight. Since this bee does not collect pollen, we may assume from it that a bee may show that much pollen on its nectar visits. I would not consider a pollen load as really mixed unless its composition established a presumption that the bee was really collecting more than one kind. Normally I do not believe polylectic bees show such a mixture except when they are changing from a flower which is going out of bloom to one just coming in, or working on scattered flowers which do not afford much pollen. I supposed this was the case of the Bombias scutellaris which I captured on Petalostemum (9). I think that a mixture of 1o per cent might readily be acquired by a nectar visit before or after beginning to collect.

Oligolectic Bees.-While they intentionally collect pollen of related flowers, they may occasionally show some admixture of other pollen. The first specimen of Ptilandrena g. maculati I ever saw was sucking on Heracleum lanatum and had her scopae filled with large pollen from Geranium maculaturn. Three species of oligolectic bees belong to nectarless flowers. In visiting other flowers for honey to mix with the pollen, they may show some admixture from flowers whose pollen they are not trying to collect. Macropis steironenatis mixes the pollen with honey at the flowers. One sucking nectar of Melilotus alba had pollen masses of Steironiema on her legs. Probably she needed to mix more honey with the pollen at the nests.

Weight of Pollen Loads.--Clements and Long have mixed three different conditions under this subject: bees which do not collect pollen, bees which mix their pollen with nectar and those not mixing it. They say (29, 128):

" The only bees able to carry a pollen load amounting approximately to half their own weight were species of Bombus; Apis, Colletes, Halictus, and Prosopis coming next with a load a third of their body weight." With Prosopis which does not collect pollen, the word " load " seems to me to be quite absurd. I do not believe that bees which do not mix the pollen with honey, like Colletes, would show as high a percentage as Apis which does. Here weight means weight of loose pollen and weight of honey and pollen.

5i8 CHARLES ROBERTISON Ecology, Vol. IX, No. t

The superiority of Boniibus to A4pis in this regard seems doubtful. I think

the high percentages are the nearest correct. Bees on their way to the nests

are the only ones likely to show full loads. Three individuals of Apis, out

of 29, show 50 per cent and over, while in 6i cases, only one Bontbus shows

as much. Of the bees I have observed, I think that the females of Calliop-

sis andreniforniiis will show the relatively heaviest loads. Since pollen mixed

with honey is evidently heavier, comparison ought to be made between those

which mix it. Those which do not mix the pollen in the field should be

compared with those which have the same habit.

Pollen Loads and EfficiencT.-It is not clear that bees which mix the

pollen with honey in the field really carry more than those which mix it at

the nest. They may be able to unload it more rapidly. The proportion of

pollen and honey in the cells may vary so that a small load of pollen may be

offset by a larger mixture of honey. Ceratina which never shows a large

pollen load may be just as efficient in providing for its young as bees which

collect more. Pr-osopis, which collects no pollen, is said to fill its cells with

a mixture of disgorged honey and pollen. It accomplishes in another way the

same result as those bees which collect pollen. For pollination, bees with

loose pollen are likely to be more efficient.

Pollination of Green Flowers.-Clements & Long (29, i95) state that

Lovell " points out that the philogeny of such flowers as developed by Bessey

(i8) strongly supports the view that they are not well adapted to pollination

by insects." According to Bessey the primitive monocotyledons were the

Apocarpae with Alisinaceae as typical and the dicotyledons were Ranales with

Raiunculaceac. The typical color was white. Green flowers were generally

flowers metamorphosed for wind pollination, Sassafras and Caulophyllum are

greenish entomophilous Ranales, but hardly typical. I have found 9i species

of insects on flowers of Sassafras and 29 on Caulophylluni. Cassia chamlae-

crista with its petiolar nectaries is about as green as a nectar-bearing plant

could be, but I have taken 66 species of insects sucking the nectaries. Salix

has flowers about as green as they could be. On 5 local species I have found

222 species of insects making 497 visits. Phytophagous insects do not seem

to have had much trouble finding any plant parts because they were green.

OTHER NOTES

Cases for Augurs.-I have seen the female of Megachile brevws sucking

nectar on 42 different flowers and collecting pollen (or both sucking and

collecting pollen) on 56 different flowers. The nectar visits may be for her

own food or to get nectar to mix with pollen for the nests. On Cassia

chamaecrista I have seen her collecting pollen on 5 occasions and cutting the

petals to line her nests on 3 occasions. Experimental auguries face some

problems here. It is fairly certain that she does not collect pollen or cut

petals except when she is making nests. Cutting petals is a peculiar habit.

Petals would be just as good for other bees to use, but they do not do so.


1 have watched the male of Aiiiegilla vaisluii flying lack and forth in a

patch of Scittellaria can escens for a long time and never alighting. To sav that it was looking for the female is about as correct a statement as the experimental atigurs could make. This is a common habit with male bees and an important thing for collectors to look out for.

It is a common thing for some insects to copulate on flowers. I have

taken Calliopsis coloradensis in copula on flowers more than all the other I1

species of Panurgidae together. I have observed Sphex grJacilis in copula on flowers very commonly, while other wasps were seldom seen together.

Climate and Temperature and Bloomiiing Scasons.-Of one group of 54

plants, i6.6 per cent bloom from April to October, while of another of 470

plants, none (lo so. The first group averages 117.3 days, the second averages 54.4 days. In October 66.6 per cent of the first group and i8.2 per cent of

the second group are in bloom. The first group has a maximum of 83.3 per cent in July and the second a maximum of 42.7 per cent in August. Of the first group, 87 per cent, while of the second, 53.4 per cent bloom in July. The first set, 10.3 per cent of the flowers observed, is always more than I0.3

per cent of the monthly floras, while the second, 89.6 per cent of the flowers. is never more than 53.4 per cent of the monthly floras. The first group forms

i6.o, 29.5 and 44.4 per cent of the March, October and November floras. The first group are introduced and their seasons correspond to the general temperature conditions. The second group are natives an(l their seasons are

the result of adj ustent to various conditions, so that they strike one as hereditary rather than as the result of temperature. The respective per-

centages in each month of natives and introduced plants are: Apr. 21.9, 22.2;

May 42.5, 5o.o; June 48.9, 83.3; July 53.4, 87.0; Aug. 51.4, 83.3; Sept. 42.7,

79.6; Oct. 18.2, 66.6. In May 35.0 per cent of the natives, and none of the

introduced flowers, end; i6.5 per cent of the natives and 44.4 per cent of the

introduced, bloom through the month. In August 59 per cent of the natives

and 88.8 per cent of the introduced are continuous. In October i6.i per cent of the natives, and 50.0 per cent of the introduced, end. Plants do not

exist in temperate regions on account of the warm summers any more than

in spite of the cold winters. Sterility of Violets a Nature Fake.-Statements that the open flowers of

violets are sterile is often repeated. The opinion seems to be based upon a

statement of Meehan (i2). In order to assure himself of this conclusion he

removed a number to his garden, where the visitors were not likely to be.

He says: " The perfect flowers, on my grounds, are not cross-fertilized by insect or any other agency. They are not fertilized at all." Of the species mentioned by him, I have found all except V. canadensis, which does not

grow here, with fruit from the petaliferous flowers. V. pedatifida and

pubescens do the same. On 5 local species I have taken 29 species of bees, Io Lepidoptera and 7 flies. I find an oligolectic bee, Iomelissa violate which

gets all of its pollen from Viola. All that Meehan did was to establish the

presumption that the flowers were pollinated by insects.

520 CHARLES ROBERTSON Ecology, Vol. IX, No.4

Lead Pencil Pollination.-Darwin (2, 12) shows a pencil with pollinia of Orchis moasculal in two positions. Miss Newell (i6) tried this on pollinia of Orchis spectab7ilis. The pollinia turned backwards instead of downwards. A female of Bomibus americanorum, which I saw extract the pollinia, im- mediately threw a front leg over them and bent them down, apparently trying to wipe them off. It was too bad, but that is what every bumblebee is likely to do.

Non-social and Social Flowers.-In Clements and Long (29, 1o6) it is said that: " In both Alliumt recurvatuwt and Heracleumt lanatum, the small- ness of the flowers is compensated by their grouping in umbels, though even this is little effective in Heracleuitn" and " In spite of the size of the clusters, however, the pinkish or white flowers of Alliun and Heracleum were obviously at a disadvantage."

It is hard to see what follows from these statements. The experiments represent the insects as dystropic. In I4, 460, I have mentioned 174 visitors of Heracleuin lanatum. The local list now numbers 254. I have found it surpassed by only Pycnanthewnum flexuosun 266, Aster cricoides villosus 297, Cicuta maculata 279 and Pastinaca sativa 292.

Although the social were only 25 per cent of the flowers observed by me at Inverness and Orlando, Florida, they received 59.2 per cent of the visits. Of 437 flowers observed at Carlinville (28, I58), the social, 45.4 per cent, received 78.9 per cent of 13,971 pollinating visits. The differences were

34.2 and 33.5. NATURAL SELECTION IGNORED, NOT REFUTED

As regards conditions of natural selection, Darwin (6) says: " The more diversified the descendants from any one species become in structure, con- stitution and habits, by so much the more will they be enabled to seize on many and widely diversified places in the polity of nature, and so be enabled to increase in numbers."

Non-selective Characters.-The existence of these is a taxonomic com- monplace insisted upon by Broca, as an objection to the theory of natural selection, and considered by Darwin.

Generic Selection

Lutz (30, 183) says it is quite improbable that the venation is a life-or- death matter to a bee, and yet differences in it distinguish genera. The im- plication seems to be that, therefore, genera are not selected.

Alph. de Candolle (6) has shown that by naturalization floras gain more in proportion of genera than of species. In Gray's " Manual," of i62 genera containing naturalized plants, ioo are additions to the flora (Darwin 6). Of the angiosperms in the 7th edition, 18.7 per cent of the genera and i6.8 per cent of the species are naturalized.

In 23 I have shown that while certain insects of New Jersey show 2.6


species to the genus, in a smaller region, Carlinville, Ill., they show 1.7. The local Bembicidae are IO.4 per cent of the North American species and 83.3 per cent of the genera. The local entomophilous flora shows about 2I.9 per cent of Gray's Manual species and about 44.I per cent of the genera. The closer the competition, the greater the generic diversification (3I, I19).

Genera of Inquilines.-Inquilines are 24.3 per cent of the local bees. Except in size somewhat according with their hosts, the genera show hardly any adaptive characters. Nearly every group, however, has distinctly adaptive food habits, being distributed as inquilines of particular groups of nest- makers: Nomadidae of Andrenidae, Pasitidae of Panurgidae, Triepeolus of Euceridae and Emphoridae, Epeolus of Colletcs, Melectidae of Anthophoridae. Sphecodini of Halictidae, Paralictus of Chloralictus, Stelidini of Osmiinae, Coelioxys of Megachilini, Psithyrus of Bombinae. Only 7 groups of nest- makers, with i8 species, have no inquilines. Does anyone suppose that these bees got their distinctive characters first and became inquilines afterwards?

Specific Selection

The usual idea of species seems to have been limited to the specific marks used in descriptions and synopses, and the theory of natural selection rejected because these were not useful. The theory of mutation seems to be based upon the assumption that the origin of species is the same as the origin of the marks. My view is that species hold definite ecological positions which determined their selection and that the marks followed, instead of preceding their separation (22 and 3I). Specific selection results from diversification of genera, of geographical range, of phenological range and food habits.

Geographical Selection.-While there are about 500 North American Andrenidae, there are 50 local species. So that nine tenths avoid competition with the local ones by having different ranges.

As stated above, in proportion as animals and plants become more closely associated in place, the percentage of the species declines and that of the genera increases. Compared with genera, geographical diversification of species is more important. Geographical diversification is an important coin- dition of natural selection.

Does anyone suppose that geographical races and species got their marks before they separated? That supposition would be no more absurd than that other species got their marks before their ecological segregation.

Diversification of Habitat.--While the local genera average I.7 species, there are a number with several species. Phenologically these overlap, but none of them coincide. Ranunculus is an example. R. fascicularis grows on dry hills, septentrionalis in low rich grounds, oblongifolius is semi-aquatic, multifidus more aquatic, aquatilis entirely so, abortivus and micranthus are annuals, one growing in rich soil and tending to become a garden weed, the other growing in drier soil. In museums,. species are put together which in nature never occur at the same time and place.

522 CHARLES ROBERTSON Ecology, Vol. IX, No. .1

Local species of Viola bloom for 84 days, 'Mar. 17- June 8, but are

simultaneous for only 8 days, Apr. 30-May 7. V. cucullata grows in open woods, pubescenis and palbiata in rich woodlands, pimiatifida and sagittata on prairies, while pcdata grows on creek bluffs. V. citcuiilata is the common-

est and palhwata the rarest. In other genera the several local species tend to

become non-competitive in blooming time and habitat. Food Habits. Of local bees 24.3 per cent are inquilines, 28.3 oligolegres,

2i.6 oligotropes and 22.6 polyleges. The ecological diversification of the

inquilines is shown in the fact that each species has its own host. Some may

compete for the same host, but I do not know of any cases.

The oligoleges show a remarkable non-competitive diversification in re-

gard to the flowers from which they get pollen. Of several American authors

who have observed flower visits of bees, Graenicher is the only one who has

seen the importance of distinguishing the pollen visits. Ignoring data show-

ing non-competitive habits, these authors would naturally incline to adopt

mutation and ignore natural selection. The oligotropes have a marked preference for different flower classes

(34), 28 being oligotropes of Hb, 4 of B, ii of B', 20 of AB, 2 of A. The polyleges vary in tongue length and those of similar tongue length

and flight-time are quite heterotropic. Of 7 polytropic Halictidae, the

maxima fall under 4 classes, and three colors (34). Three with maxima

under B' have each a maximum tinder a different color.

In the case of 182 lower Aculeata, 158 fly simultaneously, July 25-27.

But for the fact that they provision their nests with different kinds of insects,

so many species could hardly thrive in one place and fly at the same time (3I).

ILocal species with quite different food habits may be as effectually isolated

as if they had different geographical ranges.

Phlenological Selection.-The highest percentages of the bees flying simul-

taneously in each month are: May 45.9, Julne 46.2, July 47.2, August 46.6,

September 46.2, indicating that the phenological competition is as small and

as nearly equalized as possible. Before July, 30.7 per cent complete their

flight, while 25.3 per cent fly after June, 43.9 per cent overlapping. In the

case of 258 bees (296 less 14 flying from March to November, and 24 ob-

served only on i day) there were only 3 days, Sept. 15-17, when none were

beginning or ending and when the bee fauna was the same, and this was when

the times were ending, none beginning after Sept 12. Counting the season

as 2I4 days, which is the usual duration, and 296 species beginning and end-

ing their flight in that time, the composition of the bee fauna averages a

change of 2.76 species for every day. While male and female bees must necessarily have a phenological relation,

beyond certain limits they are rather competitive. In io9 cases (24) the

males and females were synchronous in only 59.2 per cent of their days.

Of 470 indigenous insect flowers, the most that are in bloom at the same


time are 42.7 per cent. There are in bloom in ay 42.3 per cent, June 48.9 July 53.1, August 51.4 and September 42.7, but never that number together

Olf the flowers of the month blooming through the month (34, 429), April shows I3.5 per cent, May i6.5, June 23.0, July 37.6, August 58.6, September

36.8. August is the only month with more than 37.6 per cent of its flowers

continuous. From April 2 to October 30 there are only three days, April I I,

August 4 and 28, when some plant is not coming in bloom or going out, and

when the flora is the same as the day before (34, 429). On the average, the

composition of the flora shows a change of 4.39 species for every day of the

season. Persons dealing with phonological data made everywhere and not much

good anywhere are likely to think that plants said to bloom in Mlay are

phenological competitors. This supposition would seem more probable from

the fact that all dominant early families have May maxima, Liliaceae,

Orchidaceae, Ranunculaceae, Cruciferae, Rosaceae, Violaceae and Um-

belliferae. But of i99 May flowers, only i6.5 per cent bloom through the

month. Local species with different phenological ranges are as effectually

isolated as if they had different geographical ranges.

Diversification of Pollinating Agenicies. Flowers having similar habitats

and about the same time may have non-competitive differences enabling them

to utilize different agencies. In 27, 72, it is stated that " flowers may be

arranged into more than 30 groups, depending upon various means of pollina-

tion. The local monocotyledons fall into nine classes, the Ranales into six

and the Polemoniales into five." Lobelia has four forms, L. cardinalis pol-

linated by birds, siphilitica by bumblebees, leptostachys and spicata by! mid-

tongued bees, and inflata by little Halictidae. Commnion and Rare Local Species.-I have taken Xcnoglossodes albata,

Emphoropsis floridana and Xylocopa virginica I, 2 and 5 times respectively,

and there are many similar cases of bees which barely extend here and never

were common. Of course there are many cases which have evidently become

rare on the road to extermination. The local Bombinae are about IO per cent

of the North American species. Their frequency is indicated by their flower

visits: Bomtlbus amnericanorurn 236, imtpatiens 145, Bontbia s separates 134,

auricomtus 87, Bomtbus vagans 68, Bomnbias .scutellaris 43, Bonibus bimtacula-

tus 24, pcnnsylvanicus (fervidits Auct.) I. In the case of 296 local bees and

6,o63 bee visits to flowers, only 44.2 per cent of the bees are in strong com-

petition, for they make 87.5 per cent of the bee visits. Knowledge of Specics.-Jordan (35) quotes Darwin's warning that " no

one should discuss species at all who has not minutely compared and described

many of them." And it is desirable that, besides their distinctive characters,

he should know their adaptive characters, geographical ranges and pheno-

logical ranges. In the case of animals he should know their food habits, and

of plants their habitats. In the case of the bees I have found many adaptive


characters none of which were mentioned in the descriptions and synoptic tables.

111utation. -Jordan says: "It is natural that one who has not realized the cumulative evidence, which shows the relation of distinctness of species to geographic isolation (' rdumliche Sonderung'), should, in contemplation of ' mutation ' and ' Mendelism ' as species formers, be ' agnostic' regarding the whole matter of the causes of evolution. For hybridism or mutation are rarely or never the basis of a species in nature. The experiments of de Vries with a garden flower, presumably a hybrid, are not typical of the ways of ' wild nature.' Several writers, especially on botany, calmly ascribe the division of genera into species to ' mutation.' We have yet to hear of any single species which could be, with any probability, regarded as having arisen by 'mutation ' or by ' Mlendelian hybridism.'"

The history of mutation seems to me to be another case where the mountain gave birth to a mouse. When persons who have become obsessed with the idea of creation of species abandon that idea, they might naturally be inclined to substitute some agent like mutation, which they speak of as acting the same way.

The fact that Oenothera laniarkiana is an introduced, or cultivated, plant seems to me quite as much of an objection to conclusions based upon it as the fact that it is an hybrid. Introduced plants behave quite differently from the natives. Their blooming seasons average I 17.3 days to the natives' 58.4 (33), more than twice as long. Mutations seem to me to be not new forms but recurring ones which have failed to hold their own.

Natural Selection. Lutz (30, 201) says: "We cannot, then, say that natural selection has not played a part in the evolution of the wing-venation of bees, but we can say with considerable confidence that it is not responsible for what we have but, at most, for what we have not." I would reverse this to say that natural selection is responsible for what we have. The natural selection of the fit and the natural extermination of the unfit are no' the same things.

Note on " Florida flowers and insects" (36) .-The best way to find errors in a paper is to publish it. On pages 280 and 307, delete T. robertsoni and E. robertsoni; 307, after T. duplicates read 2, after Elis floridanus read 39; 28i and 3I7, after Microdon viridis delete " type "; 284, line 6, read " identified " instead of " described "; 28I, after Ennyoinnta globosa insert Ex- oristoides slossonae Cq., after Phasiopsis floridensis delete " type," after Phorocera edwardsii insert P. puer WI.; 309, after Phorocera insert edwardsit i and P. puer I.

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'793

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2. Darwin, C. R. Fertilisation of orchids. ed. 2, i877.

I 870

3. Ogle, W. The fertilisation of some plants. Pop. Sci. Rev., 9: 45.

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4. Mueller, H. Befructung der Blumen. a. Fertilisation (tr. i883).

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5. Darwin, C. R. Cross- and self-fertilisation.

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6. . Origin of species. ed. 2.

i879 (7)

7. Trelease, W. Fertilization of Lobelia. Am. Nat., 13: 427.

I882

8. Lubbock, J. Ants, bees and wasps. (Romanes, Nature, 26: I2I.)

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9. Robertson, C. (9, 10). Asclepiad insects. Bot. G., 12: 207, 244.

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flowers and insects: xxv

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