TWO INSECTS OF THE OECHAED SNODGBASS. 



505 



the left and a little in advance of each point made in its course to the 

 right. Beaching the left end it loops on itself once more at e to 

 repeat the course to the right, and if it were continued in diagram B 

 a ribbed network such as that shown at A would be produced. This, 

 then, shows the simple method by which the Bucculatrix caterpillar 

 arrives at such astonishing results. The ridges are merely the ag- 

 gregate of the pointed loops, and the network between them results 

 from the two sets of threads crossing obliquely in opposite directions. 

 At the ends the caterpillar does not always make the simple loops 

 shown in the diagrams, since she interrupts the regular swing now 

 and then to run a light foundation a little in advance to which the 

 cross strands are attached. The mesh of the network is not per- 

 fectly regular since all the threads in each set are not entirely parallel 

 nor laid on exactly 

 the same distance 

 apart, yet the 

 whole is remark- 

 able for its sym- 

 metry. 



Simple as the 

 thing may appear 

 when we see how 

 it is done, let any 

 one who thinks it 

 easy attempt to 

 make a rapid, free 

 hand sketch of the 

 pattern of the co- 

 coon fabric. Con 

 fusion soon results. 

 Even after laying 

 off parallel guide lines with compass and ruler it takes much 

 practice to swing off even a fairly correct diagram with anything 

 like the speed of the caterpillar. The caterpillar, moreover, not only 

 works without guide lines but she does not do her work on paper — 

 she must bring up each sharp angle of the rib loops to just the right 

 point in empty space. The caterpillar is shown at work in figure D 

 on plate 3, but it must be remembered that in nature the cocoon is 

 nearly always built against the under surface of the support, and 

 hence has more of the nature of a hammock than of a house. Yet. if 

 the support is inverted while the caterpillar is at work, the changed 

 position in no wise interferes with her work. 



It is interesting to note here some structural peculiarities about the 

 caterpillar's feet. The first terminate each in a small, simple claw 

 (fig. 15, A) such as is common to most caterpillars, but the other two 



Fig. 15. — Thoracic legs and feet of Bucculatrix caterpillar. 

 A, Rear view of left front leg, showing exposed claw ; B, 

 rear view of left middle leg, showing split cuff protecting 

 the claw ; C, foot of middle leg more enlarged ; D, front 

 view of left hind claw and cuff. 



