THE BIRCH LEAF-ROLLING WEEVIL 



857 



only the \Vee\-irs work. Some of the 

 birch leaves are cut and rolled up in the 

 form of httle " screws," such as a grocer 

 makes of the papers which are destined 

 to hold pounds of moist sugar. A photo- 

 graph showing three of these leaves is 

 reproduced on page 856, and when such 

 leaves are detected upon a birch tree, the 

 Weevil herself is not hkely to be far off. 

 On seeing her for the first time the reader 

 will, perhaps, find it difficult to believe 

 that she can be in any way connected 

 with the tightly rolled leaves. She is so 

 insignificant — barely a quarter of an inch 

 in length ! Yet cut and roll the leaves 

 she certainly does, as the reader may 

 ascertain for himself if he be disposed to 

 watch the somewhat slow progress of her 

 labours. 



Let us suppose that we have been luck\- 

 enough to discover a Weevil about to 

 operate upon a birch leaf, and that we 

 have leisure at our disposal to witness 

 the completion of the work. The whole 

 process may take as long as two hours, 

 and it is seldom finished in less than an 

 hour and a half ; so that the watcher 

 must be prepared to draw upon his stock 

 of patience. 



I should hke, at this juncture, to em- 

 phasise the fact that it is the female 

 Wee\dl alone who engages in the ardu- 

 ous task of leaf-rolhng. He who in name 

 is her lord and master is a mere looker-on 

 — a pitiful nonentity striving to bolster 

 up authority by means of futile officious- 

 ness and senseless meddhng. I have 

 seen him stand close to his mate while she 

 is engaged in her toil, seeming to criti- 

 cise, or perhaps to offer contemptuous 

 words of advice. I have also seen him 

 turn to flee when the tide of labour sets 

 in his direction. Not that " my lady of the 

 birch" is actually aggressive. She simply 

 sweeps her slothful partner from the leaf 

 by the sheer force of ceaseless acti\-ity. 



To return, however, to the \\'eevil 

 which is about to commence rolling. First, 

 she does a deal of prospecting, moving 

 deliberately about, both upon the upper 

 and the lower surfaces of the leaf. We 

 realise that the choice of a leaf is a matter 

 of no small importance. At length, satis- 

 fied with her investigations, the insect 

 makes her way to a point at the edge of 

 the leaf, not far from the stalk, and, stand- 



109 



UPPER SIDE OF LEAF : THE BEETLE HAS 

 JUST COMPLETED ITS CUTS. 



ing upon the upper surface, makes a long, 

 curving cut with her tiny jaws from the 

 edge to the midrib. She then ascends 

 the leaf for a short distance, and from the 

 other side of the midrib makes another 

 curving cut to the opposite edge. A beetle 

 who has just completed her cutting is 

 shown in the photograph on page 859. 



In favourable circumstances this pre- 

 liminarv labour is accompUshed in from 

 ten to fifteen minutes. It is a fact worthy 

 of note that the beetle works without 

 the slightest hesitation, cutting the leaf- 

 tissue readily and continuously. Yet 

 the curved incisions, each of which 

 resemble roughly the letter S, have been 

 examined by mathematicians, who have 

 (to quote Dr. David Sharp) " extolled 

 them as being conducted on highly satis- 

 factory mathematical principles." In a 

 word, these curves are precisely those 

 which are necessary to render the subse- 

 quent rolhng of the leaf most easy of 



