2l6 



The Alder and Osier Weevil. 



[JUNE, 



on or in the bark. The larva, on hatching, feeds 

 first just below the outside bark (in thick material the 

 larva may go at once towards the wood); the bark lying 

 over this place of eating changes colour. Later this grub 

 bores into the wood, and after the gallery has been bored 

 for a short distance it takes an upward bend and runs longi- 

 tudinally in the wood for 4 or 5 inches or more. In thin 

 material the gallery may go right to the pith, but not so far 

 in thicker stems. The larval galleries are round in transverse 

 section, and are more or less filled with saw-dust and wood 



Alder and Osier Weevil {Cryptorhynchus lapathi, L.) 

 a. Weevil, x 4; ^. Larva, x 4 ; c. Tunnelled wood, showing "frass" at d, x 2. 



chips which may be seen on the outside projecting from a 

 hole gnawed by the grub in the thin superficial bark at or 

 beside the original entrance hole. The full-grown larva 

 becomes a pupa at the end of the larval boring, and the 

 beetle, on being ready, bites a round hole through the bark 

 for its exit. 



There is considerable difference of opinion as to the length 

 of the generation, and whether it be a yearly or a two-yearly 

 one. A one-year generation is the view most favoured. I 

 have at present experimental material of alder under observa- 

 tion which perhaps will help to settle the question, and am 

 of opinion that C. lapathi, just as in Nusslin's experiments 

 and my own with the allied Pissodes species, has a long egg- 

 laying period, and that there can be an over-lapping of 

 generations according to the time of laying of the egg — May- 



