CLASSIFICATION AND DESCRIPTION OF COMMON INSECTS 275 



Larva. — A whitish, cylindrical, footless maggot, tai)ering toward 

 the front, and abruptly terminated behind, where are 12 two-pointed 

 fleshy tubercles and 2 conspicuous reddish-brown spiracles; 3^:4 inch 

 long when full grown (3 to 4 weeks) (Figs. 177 and 178). 



Pupa. — Puparium in earth, oval, 3^^ inch long, chestnut-brown; 

 2 weeks in June; hibernates. 



Pig. 177. — (a) Caudal end of cabbage root maggot; {h) of the imported 

 onion maggot; and (c) of the seed-corn maggot; showing arrangement of fleshy 

 tubercles and central spiracles. All much enlarged. {After Gibson and Treherne, 

 Ent. Bui. 12, Dept. Agric. Ottawa.) 



Life-history. — Adults appear in May, when cabbages are being set 

 out, and deposit eggs. Maggots hatch in a week and feed on roots 

 for 3 or 4 weeks when they change to pupae within puparia in 

 the soil. In 15 days or so the adults appear in late June and July 

 to lay eggs for a second brood. The number of broods is uncertain, 

 probably three or four, but the later broods do but little harm. 



Fig. 178. — Cabage root maggot, side view. Enlarged 7 times. {After Gibson and 

 Treherne, Ent. Br. Can.) 



Control. — Use "single-ply tarred felt" paper disks when young 

 plants are set out; use cheese cloth frames as screens; plant trap-crops; 

 apply white hellebore or pyrethrum either as dust or as solution; 

 use carbolic wash; use corrosive sublimate solution (4 oz to 50 

 gal. water). In the case of the last three insecticides, treatment 

 should be made when the plants are set out and repeated once a week 

 for 5 weeks. 



Enemies. — Baryodma ontarionis, a Staphylinid; Cothonaspis gillettei 

 Wash., a Cynipid; and Trombidium spp. — (Consult Bull. 12, Ent. Br. 



