THE HESSIAN FLY. 53 



sites, until maturity is attained. Hence the reason \\liy vigor- 

 ous well-grown flinty stemmed varieties survive and yield a fair 

 return, while weak and sickly plants or thin-stemmed varieties 

 fail, no new stalks or shoots being formed in the fall or early 

 spring when the infested ones die, and in the early summer the 

 weak stems which have survived sink under the exhausting drain 

 of the spring brood. So far then the depredations of the Hes- 

 sian fly when not present in overwhelming numbers, may be 

 greatly lessened and in part overcome by good husbandry, and a 

 careful selection of seed of approved varieties. 



85. When the autumn maggot has arrived at its full growth, 

 its outer skin, at the approach of winter, becomes detached from 

 the body, and serves first as a larva, and ultimately as a pupa or 

 chrysalis case. This separation arises from a general contraction 

 of the body of the maggot, whereby it occupies less space than 

 the outer skin, which invested it during its growing state. The 

 outer skin now acquires a tough consistency, and a dark brown 

 colour, somewhat similar to a flax-seed in appearance, hence the 

 name of this state of the insect, which might be more properly 

 distinguished as its cased larva 

 condition. The figures (o) and 

 (n) show the position and appear- 

 ance of these ca,sed larvae of the 

 Hessian Fly (flax seed state) on 

 the stems of wheat plants from 

 which the leaves have been torn 



(PIG.O.) 



86. The maggot remains in this protecting case throughout 

 the long and cold winter months, without any marked 

 change of form, and is represented in Fig. (), which 

 shows a magnified appearance of the worm when taken 

 (FIG.*.) out of its larvae case, &c. (i) and (j). 



