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BIONOMICS OF WEEVILS OF THE GENUS SITONES 

 INJURIOUS TO LEGUMINOUS CROPS IN BRITAIN. 



By DOROTHY J. JACKSON, F.E.S. 



(With Plates XIV-XIX and 6 Text-figures.) 

 Read by Dr R. Stewart MacDougall, July 3rd, 1919. 



PART I. 

 INTRODUCTORY. 



It is well known that weevils of the genus Sitones are serious pests of 

 leguminous crops throughout the world. Their depredations have been 

 recorded on every species of clover, on vetches, lucerne, peas, beans and 

 lupins. The adults injure the plants by eating the leaves, and crops of 

 peas and beans in their early stages are often destroyed' in this manner. 



Further damage is also done to the plant by the larvae which feed 

 upon the roots. In the case of peas and beans the larvae are especially 

 destructive to the root nodules which are of such value to the plant on 

 account of the nitrogen fixing bacteria which they contain. 



In Great Britain there are several injurious species of Sitones. The 

 damage done by S. lineatus has been fully related by Miss Ormerod in 

 her Reports on Injurious Insects (li) but of the regular though less striking 

 toll effected by many of the other species on clover fields throughout 

 Great Britain much less is known. 



Examination of the existing literature on Sitones revealed the fact 

 that despite the wide distribution and the destructive habits of these 

 insects, the life-history of no single species in Great Britain was com- 

 pletely known, not even that of Sitones lineatus. Many records and 

 observations on Sitones were collected by Miss Ormerod, but unfortu- 

 nately in the majority of cases no attempt was made to establish the 

 identity of the species to which the information referred, with the result 

 that one can gain from her Reports very little definite information on 

 any one particular species. As a thorough knowledge of the life-history 

 of a pest is essential to its successful control the genus Sitones appeared 

 to me to offer a field *for investigation. I have therefore attempted to 



Ann. Biol, vn 18 



