XX. 
THE HESSIAN FLY. 
By F. Maule Campbell, F.L.S., F.Z.S., F.H.M.S., F.E.S., President. 
Read at Hertford, 24th May , 1887. 
Fig. 1. Cecidomyiadestructok, Say (Hessian Fly). Enlarged and natural size. 
The occurrences which led to the recognition of the presence 
of this pest in Great Britain were as follows. In July, 1886, 
Mr. Palmer, of Hey ell’s Hall, Hertford, noticed that his barley 
plants were nnnsnally “root-fallen.” On examination he found 
that the cause was not “ gout ” (a popular term for the distortions 
and swellings in the joints of the stems of com attacked by the 
ribbon-footed corn-fly, Chlorops tcemopus, Curtis), and that the stems 
had given way just above the second joint from the root of the 
plant. On removing the sheath he observed some small brown objects 
of a certain linear form packed close to this second joint, and in the 
direction of the axis of the plant. These were sent on the 27th of 
July to Miss E. A. Ormerod, who lost no time in visiting the fields, 
reporting that they were pupae, and as she believed those of the 
Hessian fly, or Cecidomyia destructor , Say, in consequence of their 
resemblance to the seed of linseed, which the pupae of this insect 
are so like that they are called “flax-seeds” in America and Canada. 
“On the 8th of September” (to use Miss Ormerod’s own words) 
‘ £ the first fly was developed from my ‘ flax-seeds, ’ or puparia. 
This to the naked eye was a stout-made little brown gnat, with 
darker head and body, legs of a rather lighter brown, brown horns, 
and a pair of smoky grey wings with longitudinal veins. It was 
exactly one-eighth of an inch in length.”* Miss Ormerod, after 
minute examination, had no doubt that her surmise as to the species 
was correct, and this opinion was confirmed by other entomologists. 
Meanwhile, puparia were received from Homford, Ware, Inverness, 
and Crieff, and the attack was identified on two more farms at 
Hertford, two farms at Hit chin, and one near Luton. It is difficult, 
however, to believe that the Hessian fly is confined to these localities, 
and the extent of its distribution can only be ascertained after 
agriculturists have been enabled to recognize the appearance of an 
attacked plant. Indeed, there is some reason to think that the pest 
had for two or three years infested the crops of He veil’s Hall Farm, 
* 1 The Hessian Fly,’ by Miss Ormerod, p. ii. 
