Dorothy J. Jackson 283 



or even lying more or less exposed on the earth between the plants. 

 I n the first warm clays of spring the majority migrate to peas and beans, 

 only a very few remaining upon the clover. They very soon commence 

 to lay eggs, and egg laying continues until shortly before the death of 

 the parent weevil, in the south of England at the end of June or the 

 beginning of July, and in the north of Scot la ml in August or the be- 

 ginning of September. I have never observed the adults live through 

 a second winter. The eggs hatch in 20 to 21 days and the young larvae 

 become mature in about six or seven weeks. The pupal stage lasts about 

 three weeks. The emergence of weevils is thus spread over several weeks 

 commencing in England in July, in Scotland in August. All the weevils, 

 however, emerge before the winter except in rare cases in the north of 

 Scotland, when belated specimens are to be found in the pupal stage in 

 mid-winter. The newly emerged weevils are sexually immature, the 

 ovary of the female being quite undeveloped and maturing very slowly 

 so that egg-laying does not commence till the following spring. The 

 few weevils that remain upon clover throughout the summer oviposit 

 similarly and their progeny develop in the same way, as I have proved 

 experimentally. There is thus only one generation in the year. 



Detailed Observations on Life-History and Habits. 



As already mentioned the winter is passed in the adult stage. I will 

 therefore commence to follow the life-history in detail from the time 

 when the weevils make their appearance upon the peas and beans in 

 spring, and will give an account of the field observation and breeding 

 experiments upon which my conclusions rest. The field observations 

 have been made at Wye, Kent, and in Ross-shire, and as differences 

 occur in the time of appearance of the weevil in its different stages in 

 these widely separated localities, I here record them. The breeding 

 experiments have been carried out principally in Ross-shire. For this 

 purpose flower pots were used in which the food-plant had been pre- 

 viously grown from seed, the pots being kept in a glasshouse to prevent 

 the access of "wild" Sitones before the commencement of the experi- 

 ments. A large wire ring was then attached horizontally to sticks thrust 

 in the soil at the sides of the pot and the whole sleeved with muslin, 

 the wire ring preventing the muslin from touching the leaves of the 

 plants (Plate XVIII, fig. B). These pots were always kept out of doors 

 and proved most useful for observing details of the life-history. With 

 the object of carrying out control experiments under even more natural 

 conditions, I had large breeding cages constructed 3 feet square with 



