1899] HESSIAN FLY. 37 



losses from the mere injury to the yield are increased. This diminu- 

 tion of produce may be more or less according to circumstances, but 

 damage to the heads, from their fallen position, and inconveniences 

 in harvesting from the confused state of the crop, add much to 

 troubles. 



Fig. 2, p. 36, shows the next stage of condition. After remaining 

 as above from a period variously estimated as from about twenty to 

 twenty-eight days, the white legless maggot contracts, the outer skin 

 hardens, and it changes to a somewhat flat brown 

 chrysalis-case, so exceedingly like a rather small 

 and narrow flax-seed in size and also in shape 

 and colour, that the name of *' flax-seed " is 

 commonly given to the puparium, or chrysalis-case 

 (see figure). Within this case the maggot goes 



through its changes to the perfect fly, or gnat- -5,*^ 



° , , , , , , Flax-seeds, or puparia, 



midge. This may take place so that the whole in different stages of 

 time of development from egg to fly state is only development, natural 



■ 1 , J 1-^1 L- -J ^^^^ ^^^ magmfied. 



lorty-eight days ; but the time occupied may vary 



much, some of the flies may come out the same autumn, and others, 

 threshed out, or kept in the straw, or preserved artificially for investi- 

 gation, may very likely not hatch out until May or later in the following 

 year. My own first specimen (which I conjecture to be the first of 

 which the appearance has been definitely recorded in Britain) made 

 its appearance on September 8th, 1886, from infested Barley straw 

 collected not earlier than the preceding 27th of July, and from its 

 bright red colour, by which attention was drawn to it, must have been 

 very recently developed. 



Keturning now to the condition of the maggot, or larva, after the 

 external change of its appearance to the "flax-seed" state, there are 

 some points regarding its structure brought forward by Prof. Osborn 

 (see p. 16 of his work, previously quoted), which are of considerable 

 interest. Beneath the maggot, whilst still in its general white state 

 within its newly formed brown coating, and very near tbe head, is a 

 chitinous or horny appendage, known as the "breast- 

 bone," or anchor. This process consists of a short stem 

 fixed at one end to the larva, and free at the other 

 extremity, which points forward. The fixed end is 

 placed between the first and second segments. The 

 shape of the free end is conveyed by the accompanying Breast - bone of 

 figure, which was taken by myself from life, and gives C. destructor, 

 a very fair idea of the stem of the process, which is nified. 

 about the same width for half its length, and then 

 gradually swells out, and is terminated by two conical prolongations, 

 forming together a strong fork. 



