flowers and insects: xxiv

Flowers and Insects: XXIVAuthor(s): Charles RobertsonReviewed work(s):Source: Ecology, Vol. 8, No. 1 (Jan., 1927), pp. 113-132Published by: Ecological Society of AmericaStable URL: http://www.jstor.org/stable/1929393 .Accessed: 25/08/2012 18:31

Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at .http://www.jstor.org/page/info/about/policies/terms.jsp

.JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range ofcontent in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new formsof scholarship. For more information about JSTOR, please contact [email protected].

.

Ecological Society of America is collaborating with JSTOR to digitize, preserve and extend access to Ecology.

http://www.jstor.org

http://www.jstor.org/action/showPublisher?publisherCode=esa

http://www.jstor.org/stable/1929393?origin=JSTOR-pdf

http://www.jstor.org/page/info/about/policies/terms.jsp

FLOWERS AND INSECTS. XXIV I

CHARLES ROBERTSON

Carlinville, Illinois

COLORS, CONSPICUOUSNESS AND ODOR

Bees and Different Colors.-Mueller (23, 5) says: " The most specialized, afnd especially the gregarious bees, have produced great differentiations of color, which enable them on their journeys to keep to a single species of flowers." Of I02 genera containing long-tongued bee flowers (Ma and Mlas) 5i contain only one local species and only 12 contain long-tongued bee flowers of different colors. Twenty-four genera contain 13 long-tongued bee flowers and 17 short-tongued bee flowers of a different color and i i short- tongued bee flowers of the same color.

The non-social long-tongued bee flowers (Ma) are red 56.i, white 21.4,

yellow 22.3. The differentiation is more nearly equalized in the genera, which might be expected, since natural selection operates on the most di- versified elements of the flora (3I).2 Of 38 genera with one species each, 42.1 per cent are red, 34.2 white and 23.6 yellow. Red, used in a general sense, shows a remarkable color diversification, as scarlet, blue, purple and

1ink. A considerable color diversification may occur in flowers of the same

species, as in long-tongued bee flowers: Dodecatheon miieadia and Hibiscus lasiocarpus, and in short-tongued bee flowers: Claytonia virginica, Hepatica ic tilo ba, Sisyrinchin m angfstifolium and Anewmonella thalictroides.

Dark Colors and WYasps.-Mueller (23, 298) remarks concerning Loni- cera alpigena, which he regards as a wasp flower, that it has a reddish brown color, like the flower of Scrophzularia. Knoth (I7, 120) says: "It would appear, therefore, that the brownish floral colour has a very special attraction for wasps." Of 46 visits of Vespiula and 182 of Vespidae, 58.6 and 59.3 per cent are to white flowers.

Dull Yellow Colors Avoided by Beetles.-Knuth (I7, 110, 189, 210)

makes somewhat conflicting statements on this subject. It was controverted by Bonnier in 1879 (3, 71). Schulz (34, 64) states that it is not true in the Tyrol. Pastinaca satiza was found to be visited by 42 species of beetles,

1 This paper follows Flowers and insects XXIII, Botanical Gazette, 78: 68-84. 1924.

2 The frequent citations in this paper necessitate the use of numbers corre- sponding with numbers in the list of Literature Cited, instead of the method of citing authors' names and dates as is the usual practice in this journal.

I 13

I I4 C P A RLES ROBERTSON Ecology, Vol. VIII, No. I

which is nearly twice as many as Mlueller ever found on any of the Urn- belliferae (28, 4-54). The proposition was advanced by him in 1873 (22,

103) and withdrawn in 1878 (25, 305 (35). Further discussion resulted from the fact that it was repeated in 1883 (23, 287) in a translation of 22.

It has been an anthecological dummy. Of 578 visits of beetles, 58.3 per cent are to white flowers and 32.I to yellow. They resemble short-tongtied insects in general.

Dark Colors and Flesh-flies.-The flesh-fly flowers often have dark colors, Asiniina triloba and Evonymwtus atropurpureus. But the visits of the Sarcophagidae, old group, show 63.6 per cent to white flowers and 28.2 to yellow.

Conspicuousness.-In sternotribe flowers certain petals form a banner. as in the Papilionaceae. In Gaura the four petals all turn to the upper side. In Lonicera four lobes of the corolla usually form a banner, while one forms the lower lip. The labelltim of orchids was evidently developed as a vexillum, but from inversion of the flower often serves as a landing place. In noto- tribe flowers the tipper lip often forms a conspicuous galea, but usually the lower is larger and forms a landing place as well as a vexillurn. The pendulou.s lower lip of Lobelia cardinalis is only vexillary.

Flowers usually open in sunlight and are often heliotropic, conditions increasing( their conspicuousness.

The grouping of flowers in inflorescences renders them more conspicuous. Commonly, however, this is associated with reduction in size, so that the whole cluster is no more conspicuous than a single flower of other plants. This fact seems to have been overlooked by those who find in inflorescence. only a means of increasing conspicuousness. The advantage to the plants of crowded flowers is probably in making the nectar and pollen more attractive by increasing a readily obtained supply, and in using the lower insects, 88 per cent of whose visits are to social flowers. A single head of Liatris scariosa sometimes contains forty nectar tubes and pollen from two hun- dred anthers.

The conspicuousness of inflorescences is often increased by the persistence of the old flowers, which sometimes change color and are distinguished by bees from the new ones, as in Ribes aureuMt (Delpino 8, 29). Sometimes they lose their nectar guides, Lantana. In PolOygonun the calyx retains its color until the fruit is ripe.

Sometimes the outer flowers are radially zygomorphous, increasing the conspicuousness of the inflorescence, Heracleuin, or taking upon themselves the exclusive vexillary office, Compositae. The neutral vexillary flowers are remarkably persistent. In Compositae they retain their form and color until all of the disc florets have bloomed. In Hydrangea arborescens they retain their form until late in winter. Still other inflorescences are rendered conspicuous by colored bracts: Cornus florida, Euphorbia and Castilleja coc-

January, 1927 FLOWERS AND INSECTS 115

cinea. In these the individual flowers are less conspicuous than in cases where colored bracts are absent. Species of Cornus with colored bracts have greenish petals, while those without have white petals. Analogous conditions occur in Araceae.

Knuth (I7, 83) states that stamens serve as means of allurement. In ziuzorplha the stamens supply the colors. The staminate flowers of willows are more conspicuous than the pistillate because the stamens are more conspicuous than the pistils. And this is of no use to the pistillate spikes. The staminate flowers of willows are less conspicuous than those of the anemophilous Populus deltoides, in which conspicuousness could hardly be regarded as of ecological importance.

Some flowers produce neither nectar nor pollen which can be collected, but are visited by insects in search of these substances. These are sham- nectar flowers and sham-pollen flowers. Sham-nectar flowers were distinguished by Sprengel (35, 4). They are supposed to be adapted to flies, which are stupid enough to be deceived by them. Perhaps they secrete nectar tinder favorable conditions. Calopogon parviflorus is a sham-pollen flower It is pollinated by female bees, which apparently mistake the crest on the labellum for a cluster of dehiscent stamens. As soon as they land, the label- lutm bends and lets them down upon the column. They immediately leave the flower.

Regarding conspicuousness, Mueller (23, 572) says: " The study of particular species of insects confirms the conclusion based on observation of the more conspicuous flowers, that, in general, anthophilous insects are not con- fined by hereditary instinct to certain flowers, but fly about seeking their food on whatever flowers they can find it. And hence the circumstance, already insisted on, that a flower receives the more visits the more conspicuous it is, becomes readily intelligible."

Conspicuous flowers are large and usually adapted to large insects. The majority of anthophilous insects are small. Generally small flowers can be pollinated by a greater variety of insects than large ones can. Small flowers are just as attractive to small bees as large ones are to large bees.

Mueller seems to have underestimated the insect visitors of small flowers and the flower visits of small insects. Short-tongued bees were 53.6 per cent of the bees observed by him and made 41.6 per cent of the bee visits. They are 50.6 per cent of the bees recorded here and make 50.7 per cent of the l)ee visits.

On the relation of cross-pollination to conspicuousness, Mueller (23, 570) says: "When closely allied flowers, alike in other respects differ in conspicuousness and also in the degree to which cross-fertilization is insured in case of insect visits, and self-fertilization prevented in their absence, it is always found that cross-fertilization is more perfectly insured in the more conspicuous, and therefore more abundantly visited, flowers. And on the

I i6 CHARLES ROBERTSON Ecology, Vol. VIII, No. I

other hand, under the same conditions, self-fertilization is best insured in those flowers which are least conspicuous, and which, therefore, are least visited by insects and least likely to be cross-fertilized."

Perennial plants are often larger, have larger flowers and are not dependent upon the outcome of a single season for seed production. On the other hand, many short-lived plants are small and have small flowers, but their perpetuation is intimately associated with seed production. The pres- ence of autogamy is associated with this necessity, but the so-called inconspicuousness is not associated with absence of insects in favorable weather. Such little annuals as Stcllaria media, Ellisia nyctelea, and Chaerophyllurn procumbens, are inconspicuous enough, but they are attractive to little bees. A little Chloralictus is just as efficient on Ilysanthes dubia as a big Bonibus on Pcntstemon. Ilysanthes dubia lives between the high and low-water marks, and is more dependent upon seed production. In discussions relating to the association of autogamy with inconspicuousness and of allogamy with conspicuousness, perennials must be compared with perennials, long-lived annuals with long-lived annuals, short-lived annuals with short-lived annuals.

No objection could be made to the proposition cited above, if the flowers were really alike in other respects. Mueller gives examples in 23, I55, 287, 362, 444: i. Geranium pcdustre, G. pratense. 2. G. pyrenaicum. 3. G. mnolle. 4. (C. pusillum. The last two are annuals, introduced in this country, the first probably perennials. The annuals are less dependent upon insects and often flourish where insects are rare. That facilitates migration and helps to account for the fact that 6i.i per cent of introduced plants, and only i8.5 per cent of natives, are annuals (32, 403). Heracleum spondylium, with i 8 visitors, and evidently perennial, is compared with Chaerophyllurn terlulunt, with 23 visitors, and Daucus carota which is annual and introduced here. Senccio jacobaea is compared with S. vulgaris, which is annual and naturalized in America. Veronica spicata is the first of a series ending with V. hcdcraefolia which is annual and naturalized.

Again on the effect of conspicuousness Mueller (23, 570, quoted in 30) says: "The most important deduction to be drawn from them is, that in general anthophilous insects are not limited by hereditary instinct to certain flowers, but that they wander about getting their food on whatever flowers they find it. For if each insect had its own species of flower, as most cater- pillars have their own particular food plant, the abundance of insect visits to the plant would not depend at all upon its conspicuousness." Then, after mentioning cases cited in 30 and 33, he says: " But these insects do not form I per cent of all the species that I have observed, and even of these cases the restriction is only complete in two." Of local bees (33), 28.3 per cent are oligolectic and 34.4 oligotropic, in all 62.7 per cent showing preferences.

Odor.-Odor is another of the advertising, or guiding, characteristics of entomophilous flowers. A well marked scent sometimes takes the place of

January, I927 FLOWERS AND INSECTS I 17

conspicuous colors. Agagov c irgilica, with greenish flowers, discharges its pollen and emits a strong odor just at dusk. It is much less conspicuous than most sphingophilous flowers.

Delpino (8, 39) distinguishes two groups, five classes, and 45 particular kinds of flower odors. Kerner (13, i99) estimates that there are at least 500 kinds, and distinguishes five groups. It is not easy to observe that insects prefer flowers with particular odors. No doubt they aid insects in finding flowers and in returning to those on which they are working. Nauseous odors may have had some effect in limiting the visitors, flesh-flies, indirectly, by excluding other insects. The flowers of Asiuiina triloba, which Delpino says have the odor of leaven, and the Carrion Flower, Smilax hcrbacea, are visited by flesh-flies. Asiuiina is less attractive to other insects, but certainly not more attractive to flesh-ifes than are ordinary social flowers. The same is true of So/ilax herbacca, at least the staminate flowers, on which bees are more abundant, both in number of species and individuals, and more efficient. Bumblebees do not seem to have particular objections to disagreeable smells. I have seen one crawling under a carcass, and many individuals of Boinibus aniericanorum and BI1obias aiuricominus probing among a mass of dead tadpoles, killed by the drying up of a puddle. Finally, it ap- pears that insects do not visit flowers to smell their odors.

In Europe (Mueller 23, 287) bees of the genus Prosopis are said to pos- sess a strong odor and to prefer flowers with a powerful smell. This does not seem to be true of American species.

S/hcltcr.-In plants like Arisacmna triphyllum it is a question whether the sinall Nematocera, which seem to be the principal visitors, do not enter the spathes mainly for shelter. Bees enter flowers for shelter, but it is not evident that this is important in pollination.

Protcction of Floweris.-Flowers are protected: I. By closing or remaining closed in bad weather. 2. By nodding or becoming pendulous at night or in bad weather. 3. By being constructed so that they can be opened only iby the proper visitors. 4. The disc flowers of Compositae are protected in unfavorable weather by the rays closing over them.

Flowers are protected against unbidden guests: I. By development of tufts or circles of hair inside the flower. 2. By special floral arrangements, palates, keels, hood-like galeae. But these did not keep Schulz from observ- ing I25 flowers of different species perforated by Boinbus terrester (34, 203- 24).

CONDITIONS LIMITING THE VISITS OF INSECTS

(Gonous Zygoniorphy (excluding radiate zygomorphy of Heraclcu ni and siphonate zygomorphy of Aristolochia).-Of the forms limiting insect visits to flowers, zygomorphy, perhaps, has the most decided influence. Such flowers are usually non-social, at least in the sense that each flower requires a separate visit. The nectar is concealed and usually deep-seated. The pol-

I i8 CHARLES ROBERTSON Ecology, Vol. VIII, No. I

len is usually concealed. In comparing the visits of zygomorphous and actinomorphous flowers, such forms, as Pyc 'nanthemun-l, Lycopus, Alentha, Amtorpha, Petalostemnuin, Veronica and Aristolochia tomnentosa are classed as actinomorphic. Bees make 74.5 per cent of I,124 visits to zygomorphous flowers and 40.8 of I2,847 visits to actinomorphous.

Absence of Nectar.-This condition restricts the visitors mainly to female bees, the most important to flowers of all anthophilous insects. Bees make 73.7 per cent of 244 visits to nectarless flowers and 43 per cent of 13,-

727 visits to nectar flowers. Non-social Flowers.-Next to gonous zygomorphy, the non-social con-

dition seems to have the most important effect in determining the kinds of visitors. Social flowers were first distinguished by Delphino (Apparecchi perambulatorii 9, 288). Mueller later separated a class with concealed nectar. Verhoeff (37, 175) distinguishes social flowers with exposed nectar. and Knuth (I4, 9) those with partly concealed nectar. Of insect visits to social flowers 58.6 per cent are to Umbellales and Compositae. Bees make 67.8 per cent of 2,926 visits to non-social flowers and 37.1 of I1,045

visits to social. Pendulous Flowers.-Bees are about the only insects which can visit

pendulous flowers as easily as erect ones. While flies prefer erect flowers. Asim-ina triloba, a distinct fly flower, is pendulous, and so is Evonym111Us atropurpuzreus. Pendulous flowers like these, with exposed nectar, are fly flowers; but those with concealed nectar are almost invariably melittophilous. Bees make 68 per cent of 2i6 visits to pendulous flowers and 43.2 per cent of 13,755 visits to erect ones.

P/heniology.-The principal phenological peculiarities of the anthophilous insect fauna are that the short-tongued bees are early and the long-tongued bees and lower Hymenoptera are late. The preponderance of bees before July is the result of the smaller number then of the lower Hynmenoptera. Bees make 48.7 per cent of 6,886 visits observed before July and 38.8 per cent of 7,468 observed after June.

Nectar Concealment.-An important modification is nectar so placed that only long-tongued insects can reach it. In sphingophilous flowers, the nectar is so deep seated that it is inaccessible to other insects. In others long- tongued bees can reach it. Nectar may be so exposed that long-tongued bees avoid it, while the short-tongued insects seek it. Nectar commonly rises in the tubes, so that it is accessible to many insects that can not exhaust it. This has the effect of making the adaptations of the flowers to particular insects less marked. It is not sufficient only to compare the length of the tubes with that of the tongues.

Concealment of nectar is supposed to have an important effect. Here. probably, other conditions are present, so that its importance is evidently exaggerated. The short-tubed Compositae have concealed nectar, but they

January, 1927 FLOWERS AND INSECTS II9

do not exclude any important visitors. It is necessary to compare flowers which are much alike in all other respects. Tacnidia integerrim~a, April 27-

Jutine I4, with merely concealed nectar, shows a higher percentage of bees, 42.8 to i8.9, and a lower percentage of other visitors than Eulophus aner- icanus, Mlay 12-June 13, with exposed nectar. Eryngiutut yiiccifohlunt, July ii-Aug. 30, with concealed, and a little deep-seated, nectar, shows a higher

percentage of bees, i8.i to I0.3, siphonate Diptera, and Lepidoptera, and a lower percentage of lower Hymenoptera than Cicuta inaculata, June 27- Sept. i6, with exposed nectar. Of 4,946 visits to A and AB,, bees show 34.9 per cent, while of 6,827 visits to B and B', bees show 4I.8.

In 40 groups preferring A, 30 also preferred B or B', and only 20 showed a preference for AB. This is because insects preferring A, which is usually social, are more likely to prefer B' or social B than AB which is usually non- social, the social condition having more influence than the nectar concealment.

Narrow Tuibes.-According to Mueller (23, 575) some flowers have tubes so narrow that they admit butterflies and exclude long-tongued bees. No such flowers have been observed here. Phlox glaberrirnta is the only flower observed to be visited by a number of species of butterflies and no long-tongued bees. But long-tongued bees probably occur. The narrow tubes, however, exclude a considerable number of insects.

Slender Scapes.-Small herbs with slender scapes, or stems, readily sup- p)ort the weight of small bees, but bend under the weight of large ones and bumnp them down upon the ground. Large bees are almost entirely excluded in this way.

Peculiar Flowers.-Ordinary insects are excluded by the peculiar flowers of Aristolochia torn ontosa and spathes of Arisaena triphyllurt, which admit some minute flies.

Region.-Flower visits depend upon the composition of the insect fauna. Comparing species and visits in the Alps generally and above tree limits and Low Germany (Mueller 26, 553), Pyrenees (Mac Leod 20), Flanders (AMac Leod 2I), Illinois and Florida Jan.-April, bees always gain in percentage of visits; short-tongued bees also, except in the Alps and Flanders. Flies lose, except in the Pyrenees, Flanders and Low Germany. The lower H-fymenoptera always lose, which shows that they do not belong to the same category as short-tongued bees. The Lepidoptera gain, except in the Py- renees and Low Germany.

The following table compares species (first line) and visits (second line) for highlands and lowlands:

120 CHARLES ROBERTSON Ecology, Vol. VIII, No. i

Highlands Lowlands

Flies........ 40.2-43.5 30.0-40.0 324-43.9 20.6-42.9

Lepidoptera ........ i62-30.7 6.9-I7.9 I4.1-42.8 6.9-34.9

Bees .......................................... io -,i -i6.4 17.6-24.3 I4.4-25.4 23.6-43.3

Other Hymenoptera ............................ 7.4-i6.0 19.I -25.8

4.2- 8.I 8.3-I8.0

Other visitors .................................. 7.4-I I.0 5.7-i6.7 5.0- 8.3 2.6- 9.8

Flies show maxima for species in all of the regions mentioned, but for visits they show maxima only in the Pyrenees and Flanders, while bees show maxima in Low Germany and Illinois, and Lepidoptera in the Alps and Florida.

Concealment of Pollen.-The effect of the concealment of pollen is to exclude many pollen-feeding insects and small bees which can not reach the nectar.

Peculiar Pollen.-Flowers with peculiar pollen often have oligolectic visitors whose scopae are particularly adapted to hold it (33). The tendency is toward excluding ordinary pollen-collecting bees, since they have to com- pete with bees that can collect the pollen more easily.

Closed Flowers.-The closing of the flowers by banners and keels, palates. galeae, tufts of hair, or by the petals remaining approximated, usually ex- cludes many insects which do not know how to open them, or are not strong enough.

MUELLER's FLOWER CLASSES (26, 480-503)

Flowers with Partly Concealed ANectar, AB.-Knuth says (I7, I II) It follows that flowers of this group as well as their insect visitors, are in

a distinctly higher stage of development than the flowers and insects of the previous (A) class. The degree of specialization of the insects corresponds to that of the flowers they visit." If we consider specialization in its usual sense, the flowers are the simplest, most primitive insect flowers, usually with hypogynous nectaries, and separated, or in simple inflorescences.

Before July AB, including Po, forms 22.9 per cent of the flora, and receives 26.8 per cent of the visits, but, after June, when it is 13.2 per cent of the flora, it receives only 9.i per cent of the visits. This may only indicate exaggeration in one case and neglect in the other. After June the Nomadidae, Melectoidea, Apis meillifera, Ceratinidae, Halictidae, Andrenidae, short- tongued bees, total bees, Conopidae, Syrphidae, and total visitors shift their maxima from. AB to B'.

Flowers with exposed Nectar, A.-In Rhus canadensis, April 4-May 2. bees were 69.7 per cent of the visitors, in R. glabra, MNay 27-July 7, flies were

January, 1927 FLOWERS AND INSECTS I2I

45.2, while in R. copallina, July ig-August IO, the lower flymenoptera were 39.1. In 189o (28, 457) it was shown that the kinds of visitors to flowers with exposed nectar depended upon the time of blooming.

After Jnne the Prosopididae, Empididae, Tachinidae, Diptera, Coleoptera and lower Ilymenoptera shift their maxima from A to B', really from social A to the short-tubed, mostly white, B'. Before July A shows I2.3 per cent of the flora and 24.2 per cent of the visits; after June it shows 5.7 and ii.9.

According to Knuth (17, I08) flowers of class A represent " the lowest stage of nectar flowers. Without exception they are very simple, open, and, for the most part, radially symmetrical." The stage is low only in the sense of adaptation to insects least specialized for a floral diet. Usually they have ep)igynotus nectaries and complicated inflorescences, often with different forms of flowers particularly located in them.

Pollen Flowecrs, Po.-Under this category have been mixed anemophilous flowers that are sometimes visited by insects and regular nectarless flowers with exposed pollen, while the flowers with concealed pollen have been referred to the bee flowers (26, 28). It seems erroneous to mix anemophilous with pollen flowers merely because they are sometimes visited for pollen by Ibees and Syrphids. It is probably the result of an assumption that ento- mlpl)hilouis flowers were developed from anemophilotus ones, and that some of the small, regular pollen flowers are in an intermediate stage. There seems to be no evidence of this. All of the pollen flowers mentioned here belong to entomophilotis groups, and were evidently developed from nectar flowers. Illliaceae i, Commelinaceae 3, Papaveraceae i, Nymphaeaceae 2, Malvaceae 1, Rantunctilaceae i, Primulaceae 3, Hypericaceae 3, Caprifoliaceae i.

WNVhile it is desirable to distinguish pollen flowers from nectar flowers. the category is hardly tenable as representing an ecological class. All of those consi(lered here show a well marked preponderance of bees.

Under unfavorable conditions nectar seems to be secreted in slight quantity. or not at all, so that the flowers may be mistaken for pollen flowers, HIepatica aculiloba, Podophylluuti peltatuin, Sanguinaria. canadensis, Hibiscus tirion uin, Polvgonum-it hydropiper, Samnolus floribundus, Dodecatheon inceadia. E ven Aruncus slzvester has been classed as a pollen flower (Mueller, 23, 224)

lint that is evidently a different thing from our plant. Verbascuni thapsus and Alieianehier are regarded by Knuth as doubtful, but they secrete nectar. Some flowers, like Gerardid, are evidently in a transitional stage, depending mainly upon pollen-collecting bees, but still secreting nectar in slight quantity.

Flowers woithl concealed Nectar, BS.-After June the Colletidae and He- iiptera shift their maxima from B to B', really from social B to B'. Before J uly B shows 2I.7 per cent of the flora and 21.1 per cent of the visits; after |June it shows I6.4 and 20.1.

Social Flowers with concealed Nectar, B'.-In this group Mueller included the Compositae and Eryngiumn, Valerianella and Dipsacus. Valeria-

122 CHARLES ROBERTSON Ecology, Vol. VIII, No. I

nella radiata and Dipsacus svlvestris are included here. In my classes 5i

are referred to Mas and 36 to Mis. WVhen B' changes from 8.o before July to 28.2 per cent after June, all

of the groups shift their maxima to B', except the ruby-throat and the Non- acuileata. The visits change from 10.3 to 44.8, perhaps somewhat exaggerated later.

Long-tongued Bee Flowers, Hb (including F).-The long-tongued bee flowers in general are referred to this class. After June the Bombidae, Eu- ceridae, Anthophoroidea, Osmiinae, Megachilinae, Trypetoidea, Melectoidea (ex. Nomiadidae), long-tongued bees, Panurgidae, Lepidoptera and Bom- byliidae shift their maxima from Hb to B'. Before July Hb shows 34.8 per cent of the flora and i6.9 per cent of the visits; after June 36.2 and I3.9.

FLOWER CLASSES 1

ENTOMOPHILAE (Sprengel, 35, 29; piante entomofile D, 6, 23; entornophilae M, 23, I5): insect flowers.

MIELITTOPHILAE (piante inellittofile D; melittophilae M): bee flowers. .Macromellittophilae: long-tongued bee flowers.

Anthophorophilae: Anthophora flowers. Osmiophilae: Osmia flowers. Bombophilae (Sprengel, 35; Hummelblumen M, 26, 503): bumble-

bee flowers. Megachilophilae: Megachile flowers. Mlelissodophilae: Melissodes flowers.

Xenoglossophilae: Xenoglossa flowers. Emphorophilae: Emphor flowers.

M icronmielittophilae (piante micrornelittofile D; nticronzelittophilae M): short-tongued bee flowers.

Colletophilae: Colletes flowers. Macropidophilae: Macropis flowers. Andrenophilae: Andrena flowers. Halictophilae: Halictus flowers.

AMIETAMELITTOPHILAE: metamorphosed bee flowers. Bombosphingophilae (M, 23, 264): pollinated by bumblebees and

Sphingidae. Chalcidophilae (Linnaeus, i8; Axell, I, 2): Chalcid flowers. Vespophilae (Darwin, 5, 282; Wespenblume M, 26, 395): wasp

flowers. Ichneumonophilae (M, 24, 480): Ichneumon flowers. Myiophilae (piante nniofile D; ntyiophilae M): fly flowers.

1 D = Delpino, alone =Delpino, 8, 152; Da = Delpino, 7, 33; K= Knuth, i6, 82;

M = Mueller, alone = Mueller, 23, i6.


Sapromyiophilae (piante sapromiofilc D: sapromyiophilae M): flesh-fly flowers.

Mficromyiophilae (piante mnicromtio file D; niicromnviophilac M): small-fly flowers.

Psychophilae (piante psicofile D; psychlophilae M) : butterfly flowers. Sphingophilae (Nachtblumen Sprengel, 35, I6; piante sfingofile D;

sphingophilae M): pollinated by Sphingidae. Prontibophilae (Engelmann, io; Riley, 27): Pronuba flowers. Polytropes: pollinated by various short-tongued insects.

Sphecopolytropes: the wasps predominate. Myiopolytropes: the flies predominate.

Cantharophilae (piante cantarofile D; cantharophilae M): beetle flowers.

Dientomophilae (A, 23, 545; di-entomnopliilie Errera and Gevaert, ii,

I63): with two forms pollinated by different visitors. Bomborhingiophilae (M, 23, 545): one form pollinated by bumble-

bees and another by Rhingia. Bombomelittophilae (M, 26, 30): one form pollinated by bumble-

bees and another by shorter-tongued bees. Oriiithophilae (piante ornitofile D; ornitizophilae M, 23, I5): bird

flowers. Malacophilae (piante nialacofile D; nialacophliilae M, 23, I5): snail

flowers. Chiropterophilae (Btirck, 4; Hart, I2; chiropteropitilae K) : bat

flowers. Anementomophilae (D; M, 23, 503; ancmiio-enton ophilie Errera and

Gevaert, II, I63; anentomtophilous flowers Davis, 17, io5): with an entomophilous and an anemophilous form.

Anemophilae (Wahlbom, ig; D, 7, 23; Sprengel, 35, 29; piante ane- inofile D, 6, 34; aneinophilue iVI, 23, 14): wind-pollinated flowers.

Amentiflorae (Tipo artentifloro Da; cntentiflorae K) staminate parents mobile.

Penduliflorae (Tipo pendulifloro Da; pendulxiflorae K) staminate

flowers mobile. Longistamineae (Tipo longistamineo Da; longistarnineac K;

longistaminae Davis, I7, 67): filaments mobile. Explodiflorae (Tipo esplodente Da; explodiflorae K): filaments

fly up elastically. Immotiflorae (Tipo itnunotifloro Da; itmmotiflorae K): flowers not

mobile. Hydrophilae (piante idrofile D, 7, 4; hydrophilae M, 23, 14): water-

pollinated flowers.


Hyphydrogamicae (Vaucher, 36; fecondazione subaquea D, 7, 4; hiyphydrogautlicac K) : pollinated under water.

Ephydrogamicae (fecondazione natante D, 7, 20; ephydrogaiiiicae K): pollinated on the surface.*

MELITTOPH ILAE

Delpiimo's names for flower groups are marked by their ecological pre- cision and their adaptability for cosmopolitan usage. An example of what Knith has preferred to " Melittophilae " is found in " Immenblumen." If there were many flowers adapted to Hymenoptera, the term " hymenopterid flowers " might be justified, but such is not the case. A flower visited by bees is more apt to he visited by flies and butterflies than by the other Hymen- optera. Of 417 flowers visited by bees, 62.3 per cent are also visited by flies, 4.0 by Lepidoptera and only 45.o by other Hymenoptera. There are only a few flowers that are adapted for pollination by Hymenoptera rather than by other insects. On Apocynunm., the bees and some other Hymen- optera carried pollinia, while the flies did not. Another objection to " hy- menol)teril flowers " as a general term is that those that are not bee flowers are p)rol)ably modified decendants of such. However, it might be admitted in a table of contents where one desired to give wasp flowers, Ichneumon flowers, if there are any, and Chalcid flowers an important place along with bee flowers. If there is such a thing as a " hymenopterid-lepidopterid " flower adapted to bumblebees and butterflies, why not call it a bumblebee- butterfly flower, or bombopsychophilous one?

In the following flower classes the bees, including Trochiluts, are dis- tril)uted as follows:

Long-tongued Bees.-Ant/tophora group: Anthophoridae 4, Os"iini I2, Eticeridae 7, Xylocopa I, Melectidae i, Nomadidae I; Bowmbus group: Bom- bidae io, Apis i, Trochiluts i ; Megachile group: Megachilinae 22, An- thidii1i 3, Osmiini i; Melissodes group: Euceridae 25, Emphoridae 2, M\e- lectidae i, Paranomia i.

Short-tongued Bees.-A ndrena group: Andrenidae 44, Nomadidae i8, Osmiinae 4, Colletes 3, Stelidini 2, Macropis i ; Halictus group: Halictidae 56, Ceratinidae 2.

AIACROMEL ITTOPH ILAE

Anthophora Flowers.-These bloom early and are visited principally by the first group of long-tongued bees. Several are mainly visited by Osmiini an(l might be designated as Osmiophilae, such as Collinsia verna. The

* In Flowers and Insects XXIT, Bot. Gaz. 75: 6o, it is stated that in the literature a term is credited to the one who discovered the condition, to the one who only sug- gested the term, or to the one who originated it. In an abstract in which XXII was called XXIII we find " the 'adynamandry ' of Koelreuter." The text shows that he never used the term. It is a form of Delpino's " adinamandria."


Anthophora group shows i6.5 per cent of the visitors and 30.5 per cent of the visits. Bees are 64.5 per cent of the visitors and make 78.2 per cent of the visits.

Bumiblebee Flowers.-For the class there is a slight gain for Lepidoptera. The Boinbus grotip shows 7.5 per cent of the species and 40.4 per cent of the visits.

Mlegachile Flowers.-The Megachile group shows 35.5 per cent of the species and 45.7 per cent of the visits.

Mclissodes Flowers.-The Melissodes group forms 47.5 per cent of the visitors and makes 45.4 per cent of the visits.

Non-social long-tongued Bee Flowers, Ma.-This class forms 28.3 per cent of the local flora, 30.2 per cent of the flowers observed and receives 7.5 per cent of the visits.

The colors are red 57.5, white 21.9 and yellow 20.4. Of 30 species of bees showing maxima or principal preferences under Mla, 20 showed similar maxima or preferences tinder red.

In M11a (excluding II adapted to birds and Lepidoptera) bees form 6i.2

ler cent of the visitors and make 83.4 per cent of the visits. In 5 cases bees showed 83.9 per cent of the visits and 90.4 per cent of the individuals. Ala is more homogeneous than Mueller's Hb. Bees make 71.1 per cent of the visits to Hb and 83.4 of those to Ma. Bee visits to red, white and yellow are for Hb 73.3, 62.9 and 82.8; for M4a 80.3, 91.4 and 84.4.

The Bombinae, Anthophoridae, Emphoridae and the rubythroat show maxima of visits to Mla. The visitors preferring general Ala are 31 long- tongued bees (Apis. Kby.), 4 short-tongued bees, 7 Lepidoptera and one fly, in all 35 bees and 9 other visitors.

Social long-tongueld Bee Flowers, Mas.-This class forms i6.4 per cent of the local flora, 18.7 per cent of the flowers observed and receives 20.4 pelr cent of the visits. Bees are 38 per cent of the visitors and make 54.8 peer cent of the visits. In 14 cases bees show 48 per cent of the visits and 59.3

per cent of the individuals. The colors are red 43.9, white 10.9, yellow 45.1. Of 100 species of

l)ees showing maxima or principal preferences for Mlas, 44 showed similar maxima or preferences tinder red, 9 under white and 47 under yellow. That the group is more homogeneous than Mueller's B' is shown from the fact that the percentages of visits to the different colors are more alike. Bee visits to red, white and yellow B' are 51.0, 30.3 and 45.5. Bee visits to the same colors are for Alas 54.0, 59.2 and 54.6.

Psithvrus, Eticeridae, Melectoidea (ex. Nomadidae), Megachilinae, An- thidiini, Trypetoidea, long-tongued bees, Panturgidae, Bombyliidae, Rho- palocera and Lepidoptera have maxima under Alas. The visitors preferring Mas are 73 long-tongued and 20 short-tongued bees, in all 93 bees and 83 other insects.

I26 CHARLES ROBERTSON Ecology, Vol. VIII, No.

MICRO MELITTOPH ILAE

Andrcena Flowers.-The average number of visits to non-social Andre- nophilae is 46.6. Bees are 50.2 per cent of the visitors and make 62.8 per cent of the visits.

The social show an average of 74.8 visits. Bees are 31 per cent of the visitors and make 5i per cent of the visits.

Halictus Flowers.-The non-social Halictophilae show an average of i6.9 visits. Bees are 35 per cent of the visitors and make 59.6 per cent of the visits. In i5 cases bees show 58.i per cent of the species and 73 per cent of the individuals.

The social show an average of 56.2 visits. Bees are 25.9 per cent of the visitors and make 33.8 per cent of the visits. In i9 cases bees showed 34.2 per cent of the visits and 55.i per cent of the individuals.

Non-social Short-tongued Bee Flowers, Mi.-Before July 28.3 per cent of bee visits are to Mi and these are 6i.4 per cent of the total early visits to the class. Bees make 59.7 per cent of the total visits to Mi. Mi forms 27.9 per cent of the local flora, 24.2 per cent of the flowers observed and receives 13.3 per cent of the visits. Red flowers are 14.1 per cent and yellow 35.8. Maxima under Mi are always associated with maxima under white.

On special Mi (excluding 5 Myiophilae and i Autogamae) bees are 36.8 per cent of the visitors and make 6i.2 per cent of the visits. On i6 species bees showed 59.i per cent of the visits and 74.2 per cent of the individuals. Mi has an average of i8.i visits against an average of 59.2 for Mis, social flowers of the same kind. The visitors preferring general Mi are i8 short- tongued bees, ii long-tongued bees (Apis Kby.) and 7 other insects.

Social short-tongued Bee Flowers, Mis.-This class forms 22 per cent of the local flora, 21.5 per cent of the flowers observed and receives 39.8 per cent of the visits. Red flowers are 4.2 per cent, white 65.9 and yellow 29.7.

In 43 cases showing maxima under Mis 41 showed maxima under white and 2 maxima under yellow. Bees are 25.3 per cent of the visitors to Mis and make 37.3 per cent of the visits. In 22 cases bees showed 36.3 per cent of the visits and 55.9 per cent of the individuals.

The following groups show maxima tinder Mis in general, as well as before July and after June: Ceratinidae, Nomadidae, Melectoidea, Stelidini. Halictidae, Andrenidae, Colletidae, Prosopididae, short-tongued bees, total bees, Philanthidae, Crabronidae, Scoliidae, Eumenidae, Vespidae, Sphecidae, Benmbicidae, Chrysididae, Tenthredinidae, Wasps, lower Hymenoptera, Syr- phidae, Stratiomyidae, Conopidae, Empididae, Calyptratae, Diptera, Heter- ocera (ex. Sphingidae), Coleoptera, Hemiptera, total visitors. Of the visitors preferring Mis, I27 are bees and 384 other insects. The social short- tongued bee flowers may pass into polytropic, but it requires observation of the individuals to determine that.

January, I927 FLOWERS AND INSECTS I27

METAMELITTOPH ILAE

Polytro pic Flowezrs, Pol.-This class forms 5.I per cent of the flora, 5).2 per cent of the flowers observed and receives I8.7 per cent of the visits. \White shows 78.2 per cent, and the maxima are associated with white in 9i.6 per cent of the cases. Of the visits to Pol, 36.8 per cent are made by flies, 33.3 by lower Hymenoptera and I7.6 by bees.

In the Sphecopolytropes the lower Hymenoptera, flies and bees show gains in percentages of visits over visitors. In the Myiopolytropes the flies and bees show gains.

The following groups show maxima of visits to Pol: Tiphiidae, Nys- sonidae, Larridae, Pompilidae, Evaniidae, Chalcidoidea, Figitidae, Braconi- dae, Ichneumonidae, Non-aculeata, Tabanidae, Nematocera, Acalyptratae. The visitors preferring Pol are 6 short-tongued bees and 465 other insects.

At Inverness, Florida, Fagara clava-herculis appeared to be sphecopoly- tropic, the lower Hymenoptera showing 37.5 per cent of the families, and the bees 34.3. Of i,000 individuals 654 were bees and io8 lower Hymenoptera. The short-tongued bees, forming 9.3 per cent of the families, were 48.5 per cent of the individuals. Anethun graveolens also looks like a sphecopoly- trope. Mueller (23, 283) found the lower Hymenoptera to be 54.3 per cent of the species. Of i,000 individuals taken on the flowers in my garden, 635 were bees and only 43 lower Hymenoptera. The Halictidae, mostly females sucking and collecting pollen, being only 4.3 per cent of the families, showed 58.5 per cent of the individuals. Of io8 individuals taken on Sambucus canadensis, 62.9 per cent were Halictidae females. Cases referred to Pol may really belong to Mis.

Fly Flowers.-Mueller's nauseous flowers and pitfall flowers belong to Delpino's Sapromyiophilae and Micromyiophilae.

As an example of pinch-trap fly flowers Mueller gives Asclepias. Flies make 27.I per cent of 206 visits without pollinia and only i6.2 per cent of 270 useful visits. Pinguicula and Cypripedmiun are bee flowers, not fly flowers.

The deceptive flowers seem to be quite doubtful. It may be an error that they do not secrete nectar, and that flies are exclusive on them.

It is doubtful about any flowers being adapted to, or considerably modified by Syrphidae. Exclusive visits of flower flies usually indicate that the flower is in a bad way, observed at the wrong time, or in an unfavorable situation. In the so-called Syrphid flower, Circaea lutetiana, I f ound the Syrphidae to be only i8.i per cent of ii species and 5.9 per cent of 84 individuals.

Mueller distinguished as AD some flowers with exposed nectar and showing a preponderance of flies. These are included among the Myiopoly- tropes.

9

I28 CHARLES ROBERTSON Ecology, Vol. VIII, No. I

Lepidoptcr Flowcrs.-On two species of Phlox bees showed 53.3 per cent of the visits and 70.2 per cent of the individuals, while the Lepidoptera lost i6.9 per cent.

ZoidiopHiiave.-Delpino (piante zoidiofile, 8, I5I, zoidiophilae M., 23, 14) has proposed this as a general term to include flowers adapted to insects and birds, etc., good enough, if it does not obscure the fact that flowers are typically melittophilous.

Bird Flow.ers.-Originally these were probably bumblebee flowers which have been appropriated by birds. They are bright red or scarlet. Bumble- bees can not reach the nectar. Butterflies are usually excluded by the length of the tubes and are of doubtful value when they occur.

AnementomTiophilae.-Placntago lanceolata is said by Delpino to have entomophilous and anemophilous individuals. This genus seems to be incom- pletely metamorphosed from entomophily to anemophily, not the reverse, as supposed by Delpino. P. major is the only wind flower I have seen visited for pollen by Bombus.

Aneninophilae.-According to Knuth (Is, 5I) the percentage of anemophilous plants increases with the exposure of their habitat to the wind: German flora 21.5, Schleswig-Holstein 27, Rom, Sylt, Amrum, Fohr, 36.2. Halligen 47.

The visits of bees to wind flowers are almost entirely dystropic, those of Apis mcllifera being facilitated by its ability to mix the dry pollen with honey. As a rule anemophilous flowers are diclinous and the pistillate flowers are not touched.

Hvdrophilae.-Knuth (I7, 69) says that according to Kerner (I3, 129-

31) Vallisneria forms a transition to Anemophilae. This is an adaptive sense, for there seems to be no evidence, or probability, that the Anemophilae were developed from Hydrophilae. The latter probably came from En- tomophilae. Ceratophyllum (2, 415) may have originated fromn Nym- phaeaceae.

DOMINANT GROUPS OF INSECT FLOWERS

Percentages are based upon a local flora of 560 species and I3,971 pollinating and 852 non-pollinating visits of I,288 visitors to 437 flowers.

Comnpositae (85).-This family shows 19.4 per cent of the flowers observed and 27.9 per cent of the total visits, receiving percentages of the visits of insect groups as follows: Stelidini 58.8, Epeolidae 58.5, Psithyrus 42.5, Euceridae 40.8, Megachilinae 39.5' Apis 28.3, Bombinae 25.2, Ceratini- dlae 24.7, Emphoridae 21.7, Nomadidae 14.7, Panurgidae 60.2, Colletidae 37.1I Halictidae (ex. Sphecodini) 21 .6, Sphecodini I8.9, Prosopididae i6.8, Andrenidae II.4; WNasps 30.0; ANon-aculeata 20.8; Bombyliidae 5o.8, Con- opidae 32.2, Muscoidea 28.3, Syrphidae 24.4; Heterocera (ex. Sphingidae) 57.5, Rhopalocera 36.3; Hemiptera 34.5; total insects 28.9. Bees are 29.4 per cent of the visitors and make 40.7 per cent of the visits. Bees show maxima


of visits to the following genera: Helianthlus (8) 63.6, Silph'ium (4) 63.5,

Cirsiunl (4) 57. I, Bidcns (5) 45.7, Rudbeckia (4) 38.5, Aster (9) 35.9. Flies show maxima on Erigeron (5) 39.8. The lower Hymenoptera show

maxima on Solidago (8) 34.9 and Eupatoriuni (7) 33.1. In Cacalia (3)

bees and lower Hymenoptera each show 35.1 per cent of the visits.

Uutbcllal/s (20).-Flies are 34.1 per cent of the visitors and make 36.8

per cent of the visits, while bees are I5.7 and 22.3 respectively. Bees make

360.7 per cent of the visits to Cornus. Percentages of visits of insect groups

to Umbelliferae are: Prosopididae 34.9, Sphecodini 27.9, Colletidae 14.2.

Andrenidae 12.8; Wasps 24.8, 13.9 of Scoliidae, Sphecidae, Bembicidae,

Philanthidae and Vespidae; 22.3 of Eumenidae; 42.2 of Larridae, Tiphiidae,

Pompilidae, Crabronidae, Nyssonidae and Chrysididae; Non-aculeata 57.2;

'Mnscoidea 26.6, Syrphidae 17.8, Conopidae 14.2; Coleoptera 39.4; Hemiptera

30.9; total insects i5.9. The Umbellales show 4.5 per cent of the flowers

observed and 17.3 per cent of the visits. Laiiiialcs (31).-Bees are 34.3 per cent of the visitors and make 46.6

per cent of the visits. The Labiatae receive percentages of the visits as fol-

lows: of Anthophoridae 21.3, Epeolidae i5.6, Psithyrus 14.9, Megachilinae

12.8, Euceridae i0.5, Bombinae i0.0; Sphecodini io.8; wasps I0.5, Bem-

bicidae 20.2, Larridae i6.2, Scoliidae 15.7, Sphecidae 14.8, Philanthidae 12.6;

Conopidae 10o.9; Sphingidae 13.6, Rhopalocera II.0; Rubythroat 13.7. On

Pycnanthemzunt (3) the lower Hymenoptera are 32.7 per cent of the visitors

and make 34.7 per cent of the visits, while bees are 30.3 per cent of the visi-

tors and make 3i.6 per cent of the visits. The Lamiales are 7 per cent of

the observed flowers and receive 9.4 per cent of the visits.

Leguniinosac (38). -Bees are 49.2 per cent of the visitors and make

67.8 per cent of the visits. Of Megachilinae visits I7.5 per cent, Antho-

phoridae i6.o, Osmiinae 15.2 Psithyrus 12.7, Bombinae io.6; total long- tongned bees i0.5; Rubythroat 13.7, are to Leguminosae. This family forms

8.6 per cent of the flowers observed and receives 4.6 per cent of the visits.

Polenoni'ales (26).-Bees are 59.5 per cent of the visitors and make

67.5 per cent of the visits. Percentages of visits are: of Emphoridae 28.5,

Anthophoridae io.6, Osmiinae 10.3; Sphingidae 45.4; Rubythroat 10.3. The

Polemoniales form 5.9 per cent of the observed flowers and receive 2.2 per

cent of the visits. Personages (26).-Bees are 54.4 per cent of the visitors and make 74.8

ier cent of the visits. Percentages of visits are: of Anthophoridae io.6;

Rubythroat 17.2. The Personales form 5.9 per cent of the observed flowers

and receive i.9 per cent of the visits. Rosaceae (20).-Bees are 36 per cent of the visitors and make 54 per

cent of the visits. Of Nomadidae visits 11.7 per cent, Osrniinae ii.i ; An-

drenidae i8.6, Prosopididae i2.6, Empididae 12.3, are to Rosaceae. This


family forms 4.5 per cent of the observed flowers and receives 5.9 per cent of the visits.

Salix (5).-Bees are 38.7 per cent of the visitors and make 53.I per cent of the visits. In the case of three species bees made 42.7 per cent of the visits to one form and 68.i per cent of those to both. Of the visits of Nomadidae 14.3 per cent, Andrenidae 15.7, Tenthredinidae 40.7, are to Salix. Willows form i.i per cent of the observed flowers and receive 3.8 per cent of the visits.

All observers seem to have exaggerated the importance of willows, evidently because they have many visitors easy to capture. Willows show up best along streams where other trees have been cut down and the terrestrial flora has been plowed up.

Ranales (20) .-Bees are 33.7 per cent of the visitors and make 47 per cent of the visits. On 4 species of Ranunculus bees were 5o.6 per cent of the species and made 56.4 per cent of the visits. The Ranales are 4.5 per cent of the observed flowers and receive 3.I per cent of the visits.

Cruciferae (io).-Bees, 5I.3 per cent of the visitors, make 63.2 per cent of the visits. The Cruciferae are 2.2 per cent of the observed flowers and show 2.I per cent of the visits.

Liliaceae (14).-Bees are 49.2 per cent of the visitors and make 60.3 per cent of the visits. The Liliaceae are 3.2 per cent of the flowers observed and receive i.3 per cent of the visits.

Polygonun (8).-The lower Hymenoptera, flies and bees respectively are 40.6, 3I.3 and 20.3 per cent of the visitors and make 41, 29.1 and 22 per cent of the visits. Polygonzum shows i.8 per cent of the flowers observed and i.9 per cent of the visits.

COLORS

Red.-Red flowers show for the local flora, flowers observed and visits, 29.4, 30.2 and i6.8 per cent. Visitors with maxima under red are Xylo- copidae 75.0, Emphoridae 57.I, Psithyrus 55.3, Anthophoridae 54.6, An- thidiini 44.4, Bombinae 41.I, Megachilini 40.I. Anthophoroidea 42.1, Long- tongued polyleges 37.0, Sphingidae 63.6, Rubythroat 55.i.

Of non-pollinating visits red receives 46.3 per cent, 52.1 of those of Halictidae, 53.6 of those of short-tongued bees, 42.7 of those of Syrphidae and 57.I of those of Lepidoptera.

Visitors preferring red are 6o long-tongued bees, IO short-tongued, 46 Lepidoptera, 9 flies and the rubythroat; 70 bees and 56 others.

Of total visits to red 59.7 per cent, while of those before July, 63.9 per cent, are made by bees.

Yellow.-Yellow flowers are 30.7 per cent of the flora, 30.6 per cent of the flowers observed and receive 3I.7 per cent of the visits. It is intermediate between red with i6.8 and white with 5I.3 per cent. Insects with


maxima under yellow are Melectoidea (ex. Nomadidae) 4I.I, Coelioxyini 36.3, Panurgidae 50.3, Oligoleges 50.4, Tenthredinidae 70.3, Ichneumonidae 5o.6, Bombyliidae 38.3. Yellow receives 40.6 per cent of the non-pollinating visits of beetles.

Insects preferring yellow are 43 long-tongued bees, 53 short-tongued, I33

flies, 89 lower Hymenoptera, 46 beetles, i6 Lepidoptera, io Hemiptera; 96 bees and 294 others.

Of total visits to yellow, 45.9 per cent, and of those before July 45.5 per cent, are made by bees.

White.-White flowers are 39.8 per cent of the local flora, 39.1 per cent of the flowers observed and receive 5I.3 per cent of the visits. Insects with maxima under white are Prosopididae 68.6, Stelidini 58.8, Andrenidae 54.4, Halictidae 52.o, Nomadidae 5I.I, Colletidae 50.0, Osnmiinae 48.I, Ceratinidae 47.4, Apis 43.3, Melectoidea 41.7, Coelioxys males 36.i, Trypetoidea 35.9; total bees 43.2, polyleges 44.6, inquilines 43.9; wasps 63.5, Non-aculeata 6i.7; flies 59.3; Heterocera (ex. Sphingidae) 48.i, Rhopalocera 38.6, total Lepi- loptera 39.3; Coleoptera 64.8, Hemiptera 52.2.

Insects preferring white are 43 long-tongued bees, 87 short-tongued, 253

flies, 240 lower Hymenoptera, 88 beetles, 33 Lepidoptera, i i Hemiptera-I30 bees and 625 others.

Of total visits to white, 36.6 per cent, while of those before July, 46.4 per cent are male by bees.

LITERATURE CITED (titles shortened)

I. Axell, S. i869. Fanerogama vaxternas befruktning. 2. Bentham and Hooker. i88o. Genera Plantarum, 3, pars I. 3. Bonnier, G. I879. Les Nectaires. Ann. Sci. Nat. Bot., 8. 4. Burck, W. I893. Spaziergange. Bot. G. Buit. Java. 5. Darwin, C. R. I862. Fertilisation of orchids, Ed. 2, I877. 6. Delpino, F. I867. Fecondazione piante antocarpee. 7. . I870. Dicogamia. Atti Soc. ital. sci. nat., I3 (I, 1-4). 8. . I873. Dicogamia. Atti, i6: 15I-349 (2, I-20I. I875). 9. . I874. Dicogamia. Atti, I7 (2, 20I-35I. I875).

IO. Engelmann, G. I872. Yucca. Bull. Torrey Bot. Club, 3: 33. II. Errera, L., Gevaert, G. I878. Bull. Soc. Bot. Belge, I7. 12. Hart, J. H. i897. Bull. Misc. Inf. R. Bot. G. Trin., 3. 13. Kerner v. Mar., A. I89I. N. H. Plants, 2 (1894) Tr. Pflanzenleb. 14. Knuth, P. I894. Grundriss der Blutenbiologie. 15. . I894. Blumen, Insecten, Halligen. Bot. Jaarb., 6. I6. . I898. Handbuch der Blutenbiologie, i. I7.-. (I906). Handbook of flower pollination, I. Tr. i6. I8. Linne, C. V. I744. Amoenitates Academicae, i. Cit. Axell 2.

19. -. I746. (Wahlbom, J. G.) Sponsalia Plantarum. 20. Mac Leod, J. I89I. Pyreneenbloemen. Bot. Jaarb., 3. 21. - . I893. Bloemen van Vlaanderen. Bot. Jaarb., 4. 22. Mueller, H. I873. Die Befructung der Blumen. 23. -. (I883). The fertilization of flowers. Tr. 22.

10


24. . I878. Unbewusste Blumenziuchter. Kosmos, 3. 25. . I878. Weit Beobachtungen, I, 1-59, Verh. nat. Ver. 35: 272-329.

26. . I88I. Die Alpenblumen. 27. Riley, C. V. I878. Fert. Yucca. Tr. Acad. Sci. St. L., 3. 28. Robertson, C. I890. F. and i. Umbelliferae. Tr. Acad. Sci. St. L., 5. 29. . I899. Oligotropic bees. F. and i. XIX. Bot. Gaz., 28: 27-45.

30. . 99. Oligotropic bees. III. Bot. Gaz., 28: 2I5.

3I. . I924. Conditions natural selection. Science, 59: 363-4. 32. . 1924. Phenology entomophilous flowers. Ecology, 5: 393. 33. . I925. Heterotropic bees. Ecology, 6: 4I2-36.

34. Schulz, A. I890. Bestaubungseinrichtungen, II. 35. Sprengel, C. K. 1793. Bau und Befruchtung der Blumen. 36. Vaucher, S. P. E. 1841. Histoire physiol. plantes d'Europe. 37. Verhoeff, C. 1893. Norderney. Nova Acta Leop., Halle, 6i.

flowers and insects: xxiv

Documents