1922.] 



The Turnip Gall Weevil. 



1131 



about one to four eggs per day and may lay a total of about sixty 

 eggs, visiting a number of plants for the purpose. 



In a few days the egg hatches and a small legless grub, with a 

 hardened head capsule provided with jaws, comes out. It begins 

 to feed on the inner bark and the plant reacts by growing the 

 knob-like gall around it. The head of the larva is brownish and 

 the body, which is usually held arched in the form of a crescent, 

 is whitish, but may appear yellowish in those that occur in 

 swedes. 



When this grub is fall-grown (Fig. 5 N it bores its way out of 

 the gall through a small round hole (Fig. 4), and goes into 

 the soil. With the aid of a gummy liquid w T hich it produces 

 it then makes a small mud cell (Fig. 3), and transforms inside 

 it into a pupa. These mud cells, known as cocoons, are found 

 among the roots within a depth of about 4 in. 



The pupa inside the cocoon (Fig. 6) is the stage in the life- 

 history of the insect when the grub is developing the organs 

 and structures of the adult beetle. When the pupal period is 

 over, the weevil appears, and forcing the cocoon open, finds its 

 way out. 



Two Races of the Weevils.— There are two races of these 

 beetles, each producing one brood during the year. One appears 

 in spring and breeds mostly in charlock. The parents die off by 

 summer and the young turn into beetles by August; these adults 

 do not lay eggs at once, but hibernate during the winter and 

 breed in the next spring. This race is not of much economic 

 importance. 



The other race, which may be called the summer race, 

 appears in early summer and lays eggs in cultivated crucifers 

 (cabbage, turnips, etc.) of various sorts and dies off by winter. 

 The eggs soon hatch into grubs and these remain in the galls 

 during the winter and pupate in spring. This race is of great 

 importance to the farmer. 



Life-History of the Weevils of the Summer Race.— The 

 parent beetles make their appearance about the beginning of 

 June, lay eggs from the end of August throughout autumn, 

 and die off in winter. ^Turnips in all stages and other plants 

 about six weeks old are preferred for laying eggs in. The eggs 

 hatch in five days or more according to the weather conditions, 

 longer periods being necessary if it is cold. The larvae in various 

 stages hibernate in the galls during winter, resume feeding in 

 spring, and throughout March and April and one after another 

 leave the galls and pupate. The full-fed larvae do not bore 



