We have become accustomed to call insects which are attracted to flowers anthophilous.
Almost all of the anthophilous insects belong to the highest groups of the entomological fauna,- to those whose metamorphoses are complete. The more primitive orders appeared in the world in an epoch when flowering plants did not yet exist, and therefore they did not have to adapt themselves to flowers. Aside from Neuroptera of the family Thripsid and the true bugs of the genus Anthocoris, insects whose metamorphoses are incomplete do not rob flowers. With some rare exceptions, we can say the same thing about larvae of all the orders. Even in the order Coleoptera, where, however, the metamorphoses are complete, the frequenting of flowers is exceptional. With the Cetonians which browse on petals and pollen, with Saprinus which visits vile-smelling flowers, and with the little Meligethes which swarm in 200 corollas, the grinding-apparatus of the mouth is not modified, although it becomes elongated and already presents an adaptation to flowers with certain longicorns, notably with the genus Strangolici.
When it elongates into a beak, as in the bee-flies and the mosquitos, or when it spreads out into spongy lobes as in the house fly, the buccal apparatus of the Diptera is wonderfully adapted to collecting liquids. Indeed, the Diptera are almost all flower-freqtienters. Certain of them, such as the bee-flies, collect the nectar while flying; others, like the Syrphid, feed at rest, collecting at the same time nectar and pollen.
This adaptation to flowers is closer still with the Lepidoptera. Aside from the moths of the genus Micropteryx, which have preserved the mouth parts of the Neuroptera, they have a long tube-like beak which permits them to suck up liquids and consequently also the nectar of flowers. The beak is commonly so long that it is rolled into a spiral when the insect is at rest. It reaches its maximum with the SpJiingidce, which drink during flight in the same way as the bee-flies. It is also a very plastic organ, capable of playing other roles. As Kiinckel d'Herculais has shown (1916), it becomes an inflexible stylet with Ackerontia, or the death's-head moth, which employs it to reach the honey in cells, and with the exotic noctuids of the genus Ophideres, by which it is used to puncture fruit.
All the Hymenoptera are fond of nectar, but certain of them not only collect the floral products for their own use, but gather them also for their larvae, so that the whole existence of the insects is bound up with flowers. So it is with the solitary wasps of the Masarian tribe and in the vast group of Mellifers, or bees. The progressive adaptation of the collecting-apparatus is very striking in this last group. With the solitary bees of the genus Prosopis the mouth parts do not differ from those of other Hymenoptera, and it is with their lower lip, short and bilobed, that these insects collect nectar and pollen which they disgorge afterward to their larvae in the form of a paste. With Colletés the skin is covered with hairs to which pollen attaches itself and is afterward brushed off and mingled with the nectar to make porridge for the larvae. With the Halycti and the Andrenas there is a double progression. The hind legs possess a tuft of long hairs for the collection of pollen, and the lower lip is elongated into a beak for the collection of nectar. It is elongated still more with other Mellifera, in which, combined with the jaws, it becomes a capillary tube that folds into a Z when the creature is at rest. And, further, the pollen apparatus becomes a ventral brush with the solitary bees of the genera Osmia and Chalicodoma. It is also similar in the Halycti, in the Xylocopas and the An-thophoras, while it acquires a high degree of perfection with the social bees, namely the bumblebees, the Melliponas, and the true bees properly so called. Unlike the solitary forms, these insects moisten the pollen with their mouth at the moment of collection, and make cakes of it which they attach to a depression or comb situated on the external face of the tibiae of their hind legs. And to facilitate the agglomeration of the pollen dust, the following segment is much enlarged and on its internal face is a brush with short hairs and ridges in parallel series. The adaptation to the anthophilous regimen is perfect.
Whatever its beginning may have been, or however completely realized it has become, the adaptation of the Mellifera to flowers is sufficient and is necessary. Without doubt these insects are fond of all sugary material, even the honey-dew from the 'leaves or the honey-dew of plant-lice ; but with the bees that is an accessory resource, and we may well say, with Perez, that "all the species of[ bees would disappear without exception if iflowers ceased to exist or if they ceased to produce nectar and pollen. '9