HESSIAN FLY. 



83 



1, Anchor-process of 

 larva of C. destntctor ; 

 2, of C. tritici (mag- 

 nified). 



is a very convenient way of knowing this kind of larva from 

 those of the common fly maggots (dipterous larvae) which 

 infest Corn. The process consists of a 

 short stem fixed at one end to the larva 

 and free at the other, which is enlarged 

 and of very variable form. 



The use of this appendage does not 

 appear as yet to be fully known, but from 

 my own observations I conjecture that 

 it is used as a digger or scraper to assist 

 the excessively delicate mouth-parts in 

 acquiring their food from the stem. 



It appears from Dr. Lindeman's care- 

 ful observations in Eussia that the larva 

 (or maggot) lives about twenty-eight 

 days in this condition. Then it changes 

 at the precise spot at which it fed to a 

 brown flat chrysalis, in size and shape 

 and colour strongly resembling a rather 

 small and narrow flax-seed, whence the 

 name of " flax-seeds " is commonly given 

 to these chrysalis-cases or puparia. At 

 first, as will be seen by the figures, these 

 puparia are smooth on the surface, but 

 gradually become wrinkled longitudi- 

 nally. Within this hard outer husk the maggot changes to 

 chrysalis, and the chrysalis to the perfect fly, but how long 

 this may take depends very much on circumstances. It 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 ; but it has 

 been shown that if the puparium — to give it the precise name 

 — is put in unfavourable circumstances, development may be 

 greatly retarded. Thus, some of the flies may come out in 

 autumn in the fields, and others threshed out, or stacked in 

 the straw, or kept artificially for investigation, may very likely 

 not hatch until May, or much later in the following year. 



The perfect fly much resembles a stout-made little brown 

 gnat, about one-eighth of an inch in length, with one pair of 

 smoky-grey wings, and with long horns. (See fig., p. 80).* 



At present we have no reason to suppose that we suffer in 

 this country from Hessian Fly attack to the young autumn- 

 sown Wheat-plant. In this form of attack the maggot (from 



* A full scientific description of the male and female fly, taken from living 

 specimens, by Mr. R. H. Meade, of Bradford, will be found in the number of 

 the ' Entomologist ' for July, 1887, and also in my ' Eeport on Injurious 

 Insects ' for that year. Published in both cases by Simpkin & Co. London. 



g2 



"Flax-seeds" or pu- 

 paria in difierent stages 

 of development, nat. size 

 and magnified. 



