44 LEAF-MINING INSECTS 



spinneret having the form of a small, elongate nipple considerably- 

 like those of ordinary caterpillars. This spinneret is difficult to 

 see but nevertheless I saw it quite plainly with a long thread that 

 the caterpillar had just spun still attached 



In order to see the very remarkable legs it is necessary to look 

 at the caterpillar from the side with the help of a strong lens. 

 They are eighteen in number and placed all along the under side 

 of the body in two rows. They are very like the membranous 

 legs of saw-fly larvae; their shape is pyramidal or conical, and 

 they are entirely without hooks. They differ from the legs of 

 other caterpillars even in their arrangement on the insect's body; 

 for they are placed on the nine consecutive segments which follow 

 immediately after the first, and each of the nine segments has a 

 pair of them. It is, then, the first, the eleventh and the twelfth 

 or last segments which lack legs. 



I looked at these caterpillars many times, and I looked at many 

 of them in order to make myself sure of the number and appear- 

 ance of their legs. That was in the year 1737. But I was not 

 satisfied even with that; nine years afterward, in 1746, I repeated 

 my observations, I examined afresh the legs of the caterpillars of 

 this species and again I found them exactly as just described. One 

 cannot sufficiently verify new and singular observations. 



These caterpillars mine as we have said, in the interior of leaves 

 where they make a sort of tunnel. One may find leaves with 

 three different tunnels, mined by three caterpillars ; but ordinarily 

 each leaf is inhabited by one. The transparency of the upper 

 membrane makes it possible to see the insect through it. 



To see whether the leaves are mined one must look at them 

 from above, for the insect mines them in such a way that on that 

 side there remains only the membrane; the lower side retains a 

 part of the fleshy substance, the caterpillars consuming but half 

 the thickness of the pulp within the leaf. But by holding the 

 leaf up to the light one can see equally from either side whether it 

 is inhabited. With the help of a lens one may also see in this way 

 how the caterpillar mines the leaf. One may see how with the 

 two teeth that it has in its mouth it bites into the fleshy substance, 

 how it loosens, piece after piece in succession, tiny bits that it 

 immediately swallows. 



