292 



COLEOPTERA 



CHAP. 



whole of a leaf is not iised in the formation of a funnel, cuts being 

 made across .the leaf in suitable directions. The beetle stand- 

 ing on a leaf, as shown in the figure, proceeds to cut with its 

 mandibles an incision shaped like an erect S, commencing at a 

 certain part of the circumference, and ending at the midrib of the 

 leaf; the beetle then goes to the other side of the midrib, and 

 continues its incision so as to form another S-like curve con- 

 siderably different from the first ; being prostrate and less abrupt. 

 Thus the blade of the leaf is divided into two halves by certain 

 curved incisions, the midrib remaining intact. The little funiiel- 



FIG. 149. The leaf-rolling of Rhynchites betulae. Britain. A, Female beetle, magnified ; 

 B, the beetle forming the first incision on a leaf ; C, the completed roll. (B and C 

 after Debey. ) 



twister now commences to roll up the leaf to form the funnel ; 

 and this part of the work is greatly facilitated by the shape of 

 the incisions. Going back to the spot where it commenced work, 

 by the aid of its legs it rolls one side of the leaf round an ideal 

 axis, somewhat on the same plan as that adopted by a grocer in form- 

 ing a paper-funnel for sugar. The incisions are found to be just 

 of the right shape to make the overlaps in the rolling, and to re- 

 tain them rolled-up with the least tendency to spring back. After 

 some other operations destined to facilitate subsequent parts of its 

 task, the beetle enters the rolled-up part of the leaf and brings it 

 more perfectly together ; it again comes out and, pursuing a 

 different system, holds on with the legs of one side of the bodv 



