46 FLIES. 



The attack may be to the young plant, but with us 

 it mostly occurs only as a summer infestation to the 

 growing stalk, where the small white legless maggot 

 (which is much of the size and shape of the puparia 

 given below, nat. size and mag.) feeds outside the stalk, 

 but inside the leaf-sheath just a little above one of the 

 knots. Commonly it is just above the second knot, 

 but the attack may occur lower down at the first knot, 

 or close to the root, or higher up above the third or 

 fourth knot. 



The mark of attack being present is the stem 

 elbowing sharply down just above where the maggot 

 lies. It does not commonly break, but, unless the 

 straw is very firm, it bends at the weakened spot, and 

 thus damage is caused to the fallen head, besides 

 difticulty in reaping from the confused state of the 

 straw. (See Fig. 41, p. 45.) 



The maggot may live for about four weeks in this 

 position, and then it changes, at the spot at which it 

 fed, to a flat brown chrysalis, in 

 size and shape and colour minutely 

 resembling a rather small and 

 f\ ^ • 11 fj^ ^^ik^ I'^arrow flax-seed, whence the name 

 U M'l" I ^ Ml III ^^ "flax-seeds" is commonly given 

 to these chrysalis-cases or j?//jja7-/a. 

 Within this hard outer husk the 

 Eo ~ ' maggot changes to chrysalis, and 



FiG.42.— "Elax-seeds" the chrysalis to the perfect fly, but 

 or puparia in differ- j^^^ ^ ^^^^g ^^^^ depends 



ent stages of deve- '=', . -^ ^ ^ ^. 



lopment, nat. size very much on cu'cumstances. It 

 and magnified. may occur, under natural and 



favourable circumstances, so soon 

 that the whole time occupied in the life of the fly from 

 egg to development is only about forty-eight days ; or 

 under unfavourable circumstances it may be retarded. 

 Thus some of the Hessian Flies may come out in 

 autumn on the fields ; whilst some of the " flax-seeds " 

 threshed out, or stacked in the straw, or kept artifici- 

 ally for investigation, may very likely not hatch until 

 May, or much later in the following year. 



