INSECTS IN RELATION TO PLANTS 



269 



FIG. 262. 



Modifications of Insects with Reference to Flowers. 



While the manifold and exquisite adaptations of the flower for 

 cross pollination have engaged universal attention, very little 

 has been recorded concerning the adaptations of insects in re- 

 lation to flowers. In fact, the adapta- 

 tion is largely one-sided; flowers have 

 become adjusted to the structure of in- 

 sects as a matter of vital necessity to 

 put it that way while insects 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 adapta- 

 tions for gathering and using pollen and 

 nectar. 



Among mandibulate insects, beetles 

 and caterpillars that eat the floral en- 

 velopes show no special modifications 

 for this purpose; pollen-feeding beetles, 

 however, usually have the mouth parts 

 densely clothed with hairs,' as in Euphoria (Fig. 261). In 

 suctorial insects, the mouth parts are frequently formed with 

 reference to floral structure; this is the case in many but- 

 terflies and particularly in Sphingidse, 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 Syrphidse, Stratyomyiidse and Muscidae are specially 

 adapted for feeding on pollen. In Apidse, the tongue as com- 

 pared with that of other Hymenoptera, is exceptionally long, 

 enabling the insect to reach deep into a flower, and is exqui- 

 sitely 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 



Pollen-gathering hair 

 from a worker honey 

 bee, with a pollen grain 

 attached. Greatly mag- 

 nified. 



