THE BIRCH LEAF-ROLLING WEEVIL 



859 



THE ROLLING ALMOST COMPLETE. AT THIS STAGE 

 THE BEETLE LAYS ITS EGGS WITHIN THE LEAF. 



creeps up the birch stems. From these 

 facts the reader will perceive that the 

 newly emerged Weevil cannot, by any 

 conceivable chance, have seen a rolled 

 birch leaf. Thus, it is plain that imi- 

 tation plays no part in the subsequent 

 procedure of the insect. The elaborate 

 cutting and rolling in which the Weevil 

 engages can be explained only by 

 employing the word " instinct," and this, 

 as the reader will be well aware, is really 

 no explanation at all. 



The Birch Leaf-rolling Weevil is by no 

 means the only English beetle which rolls 

 up leaves. Nor does it confine its activi- 

 ties to birch trees. It may often be found 

 hard at work upon alder bushes. ]\Iore- 

 over, there are two species of the family 

 AttclahidcB — both of them beautiful, coral- 

 red insects considerably larger than Rhyn- 

 chites hetiilcB — which roll up oak leaves 

 and hazel leaves, each species accom- 



plishing its work in a different and 

 characteristic manner. These two 

 beetles may be described as "locally 

 common" — i.e. they are not always 

 to be found when wanted, but when 

 found they will be present in numbers. 

 The writer has often observed the 

 manner in which Atielahns citrcii- 

 lionides rolls up its oak leaves, but 

 considerations of space prevent a de- 

 tailed description of its methods 

 being added. Suffice it to say, that 

 the insect proves itself equal in in- 

 genuity to its relative of the birch 

 tree, and that its roUed-up leaf, when 

 finished, resembles a small thimble, 

 or barrel, rather than a screw. 



Exactly why these Weevils adopt 

 the plan of leaf-rolhng as a means of 

 providing food and shelter for their 

 grubs is not definitely known. Quite 

 a number of species, which actually 

 belong to the same genera, do not 

 roll leaves at all. For example, a 

 species of Rhynchites which is some- 

 times fairly abundant on hazel 

 bushes, merely pierces the top shoots 

 of that plant so as to arrest their 

 growth, after ha\ang deposited an egg 

 in each of them. Other species lay 

 their eggs in the recently formed fruit 

 of wild trees, afterwards duly making 

 an incision in the stalk below, so 

 that the fruit fails to develop 



properly, and ultimately falls to the 



ground, where it continues to pro\'ide 



nourishment for the grub within. It 



is thus perfectly clear that leaf-roll- 



ing is by 



no means 



essential to 



t h e w e 1 1- 



being of these 



insects, and 



why some of 



the species 



should have 



acquired the 



habit is a pro- 



b 1 e m which 



must be left 



unsolved 



pending the 



further ad- 

 vance O i BIRCH LEAF-ROLLING WEEVJL. 



science. (Magnified.) 



