IXTERDEPEXDEXCE OF ORGAXISMS 



23 



It is a part of the fitness of things 

 that these brushes are usually best de- 

 veloped on the top of the thorax, the 

 under surface of the abdomen (fig. 17) 

 and the outer faces of the legs — the places 

 of most frequent contact with anthers 

 and stigmas : but special tufts of hair or 

 scales are occasionally found in unusual 

 places, serving the needs of some partic- 

 ular flower. The hairs of many bees 

 and syrphus flies bear numerous mi- 

 croscopic lateral branches and hold pol- 

 len grains the more securely in the angles 

 of the branchlets (fig. 18). The hairs 

 may gather of themselves sufficient pol- 

 len to be worthy of consideration as 

 food: but the pollen must then be 

 gathered up and massed together, and for this purpose 

 "pollen combs" (fig. 19) are developed upon the inner face 

 of the enormously enlarged basal joint of the hind torsus 

 of bees, and a "pollen basket" is developed on the outside 

 of each hind leg. 



Fig. 19. Hind leg of 

 bee, ex, coxa; tr, 

 trochanter;/, femur 

 I, tibia; i, 2, 3, 4, 5, 

 segments of the 

 tarsus; i, carrying 

 the "pollen combs." 



Other parts. — The modifications of other parts of the in- 

 sect, antennae, wings and legs, have to do chiefly with ac- 

 commodating it to entering corollas. Obviously the but- 

 terfly shown in figure 20 could not enter, and does not need 

 to enter bodily into a flower. The bee will again illustrate 

 by what means the antennae have been made reversible, 

 the legs, closely applicable to the sides of the body, and 

 the wings, close-folding upon the back; the whole insect 

 compacted together, and admirably fitted for getting into, 

 and for getting out again from, the tight places on the 

 road to the nectar in specialized corollas. 



