INSECTS : THEIR FEET. 123 



as /. Xiphium, require the agency of the larger humble- 

 bees, which alone are strong enough to force their way 

 beneath the style-flag ; and hence, as these insects are 

 not so common as many others, this Iris is often barren, 

 or bears imperfect seeds." * 



The legs and feet of Caterpillars are constructed on 

 a very different plan from those of perfect insects, as 

 you may see in this living Silkworm. The first three 

 segments of the body, reckoning from the head, are 

 furnished each with a pair of short curved limbs set close 

 together on the under side. These represent the true 

 legs of the future moth, and show, notwithstanding 

 their shortness, four distinct joints, of which the last is 

 a little pointed horny claw. The whole limb resembles 

 a short stout hook. Then two segments occur which 

 are quite smooth beneath, and destitute of limbs; and 

 then on the sixth we begin to find another series, which 

 goes on regularly, a pair on each segment, to the eleventh 

 and final one, with the single exception of the tenth 

 segment, which is again deprived of limbs. 



But these organs are of a very peculiar character. 

 They have no representatives in the mature insect, but 

 disappear with the larva state; and they are not con- 

 sidered limbs-proper at all, but merely accessory develop- 

 ments of the skin to serve a special purpose. They are 

 sometimes called claspers, sometimes false-legs, but more 

 commonly pro-legs. 



Each consists of a fleshy wart, which is capable to 

 some extent of being turned inside out, like the finger 

 of a glove. Partly around the blunt and truncate 

 extremity are set two rows of minute hooks, occupying 

 the side next the middle line of the caterpillar in a 

 semicircle alon^ the mannn. These hooks arch outward 



* Penny Cyclop., art. Bee. The researches of the late Mr. Darwin 

 and others have shown that the agency of insects in the fertilization 

 of plants is very far more important than had been suspected. 



