100 Weevils of the Germs Sitona 



Life-History. 



The life-history of most of the SUona which breed upon clover is 

 complicated by the long period of egg-laying of each female, with the 

 result that the development of the progeny of the same parent extends 

 over a considerable time. The life-history of S. hispidula may be thus 

 summarised. There is only one generation in the year. The imagines lived 

 about 12 months. They emerged from the pupal stage from July to 

 September and commenced to lay eggs six to eight weeks after emergence. 

 A few eggs were laid during the winter and vigorous oviposition recom- 

 menced in spring. Towards the end of June egg-laying decreased, and 

 during July most of the weevils died. Eggs laid late in autumn did not 

 hatch till the following spring, but a few of the September eggs and all 

 those laid in spring and summer hatched in 25 days. No success was 

 obtained in rearing the few larvae which hatched in autumn from the 

 first laid eggs, but those which hatched in the following spring and 

 summer fed up in from 11 to 14 weeks, pupated, and emerged as adults 

 four weeks later. The last few eggs laid by the old females in July pro- 

 duced full fed larvae and pupae in the end of October, but these perished 

 during the winter. Thus it will be seen that the principal period during 

 which the larvae occur is in the summer from the end of April until 

 August, those larvae which hatch before the winter from the first laid 

 eggs and those which hatch late in the following summer from the last 

 laid eggs of the same parents being few in number and uncertain in 

 attaining maturity. The winter is thus passed almost entirely in the egg 

 and imaginal state. 



Detailed Observations on Life-History and Habits. 



The Ufe-history has been ascertained by field observations and 

 breeding experiments. These may be placed in three groups according 

 as they relate (1) to the imagines, (2) to the length of the egg stage, and 

 (3) to the length of the larval and pupal period. 



I. The Imayines. 

 Length of Life and Period of Oviposition. 

 [a) Field Observations. 



Adult S. hispidula were obtained from various localities at different 

 times of the year. If sexually mature the females laid eggs readily in the 

 boxes in which they were collected. They were never subjected to artificial 

 temperature. If immature, the beetles were sleeved in musUn bags upon 



