Oak-bark Caterpillars. 



217 



divided into thirteen segments. Their head is large and 

 convex.* 



It would not be easy to find a more striking example of 

 ingenuity than occurs in a small caterpillar which may 

 be found in May, on the oak, and is supposed by Kirby 

 and Spence to be that of the Pyralis strigulalis. It is of 

 a whitish-yellow colour, tinged with a shade of carnation, 

 and studded with tufts of red hairs on each segment, and 

 two brown spots behind the head. It has fourteen feet, 

 and the upper part of its body is much flatter than is 

 common in caterpillars. When this ingenious little insect 

 begins to form its cell, it selects a smooth young branch 

 of the oak, near an offgoing of the branchlets whose angle 

 may afford it some protection. It then measures out, with 

 its body for a rule, the space destined for its structure, the 



Magnified Cells of Pyralis strigulalis? 



a. The walls before they are joined, b. Walls joined, but not closed at top. c. Side 

 view of structure complete. 



basement of which is of a triangular form, with the apex 

 at the lower end. The building itself is composed of 

 small, rectangular, strap-shaped pieces of the outer bark of 

 the branch cut out from the immediate vicinity ; the insect 



* Kirby, in ' Linn. Trans.,' vol. v. p. 246, and Introd. 11. 



