INSECTS IN RELATION TO PLANTS 



of insects as a matter of vital necessity to put it that way while in- 

 sects have had no such urgent need so to speak in relation to floral 

 structure. They have been influenced by floral structure to some extent, 

 however, and in some cases to a very great extent, as appears from their 

 structural and physiological adaptations for gathering and using pollen 

 and nectar. 



Among mandibulate insects, beetles and caterpillars that eat the 

 floral envelopes show no special modifications for this purpose; pollen- 

 feeding beetles, however, usually have the mouth parts densely clothed 

 with hairs, as in Euphoria (Fig. 262). In suctorial insects, the mouth 



FIG. 262. A, right mandiWe; B, right maxilla; C, FIG. 263. Pollen-gather- 



hypopharynx, of a pollen-eating beetle, Euphoria inda. En- ing hair from a worker honey 

 larged. (The mandibles are remarkable in being two-lobed.) bee, with a pollen grain at- 

 tached. Greatly magnified. 



parts are frequently formed with reference to floral structure; this is the 

 case in many butterflies and particularly in Sphingidae, in which the 

 length of the tongue bears a direct relation to the depth of the nectary 

 in the flowers that they visit. According to Miiller, the mouth parts of 

 Syrphidae, Stratyomyiidae and Muscidae are specially adapted for feed- 

 ing on pollen,. In Apidae, the tongue as compared with that of other 

 Hymenoptera, is exceptionally long, enabling the insect to reach deep 

 into a flower, and is exquisitely specialized (Fig. 127) for lapping up and 

 sucking in nectar. 



Pollen-gathering flies and bees collect pollen in the hairs of the body 

 or the legs; these hairs, especially dense and often twisted or branched 

 15 



