118 On the Life Historij of " Wireworms'' 



winter conditions and in order to give the larvae more scope for move- 

 ment, the soil and grass plants from the small pots which contained 

 larvae were bodily transferred to larger glazed earthenware pots con- 

 taining more soil. These pots are the usual long pots used at Rothamsted 

 for botanical and other pot work. They measure some 15 inches in 

 length, 5 inches in diameter, and have a lateral bung-hole about one 

 inch from the bottom. It was intended to sink these pots in the soil, 

 bringing the soil-level in the pot to that of the surrounding ground. 

 After experiment, however, great difficulty was experienced in draining 

 the water from the pots without risk of the larvae escaping, so the pots 

 were dug up and transferred to a lean-to shed facing North, Here they 

 remained during the winter and the larvae, at least those of Agriotes 

 obscurus, have successfully withstood the rigour of three winters under 

 these conditions. In the summer the pots were transferred to the open 

 and watered sufficiently to keep alive the plants of grass growing on the 

 surface. For the first eighteen months no further supply of food was 

 introduced, but in the spring and summer of 1918, a few slices of potato 

 were given and have been eaten by the larvae. 



In addition to the larvae bred from the egg, wild-caught larvae have 

 been kept, in the laboratory chiefly, for observation. Owung to their 

 predilection for a diet of their own kind, especially at times of moulting, 

 it has been found necessary to keep each individual larva separate. 

 Round tin "pill-boxes" or "salve boxes" have been used for this 

 purpose, each larva being placed in a piece of turf or soil and supplied 

 with food from time to time. It is necessary however to exercise care 

 in giving sufficient water, for, as is well known, wire worms are excess- 

 ively prone to desiccation and the soil must not therefore be allowed to 

 become dry. 



It is not pretended that these laboratory-reared larvae are reared 

 under anything approaching natural conditions, but certain points have 

 been elucidated by this method and wherever there is reason to doubt 

 that observations made under such conditions would be different in the 

 field, they can usually be checked. 



I have obtained larvae from several different sources, the principal 

 ones, beside the local ones of Harpenden, being Cambridge and Winder- 

 mere. 



From the latter place an almost unlimited supply has been obtained 

 from heaps of stacked sods, originally taken from a meadow on its con- 

 version into garden. Many pupae and newly emerged adults, principally 

 of Agriotes obscurus, have also been taken from the same place. 



