1899] HESSIAN FLY. 33 



" Hessian Ply." Cecidomijia destructor, Say. 



B*EO 



Cecidomyia destkuctoe, Hessian Fly, nat. size and magnified. 



In the past season when, from tlie conditions of the weather during 

 many weeks of the summer being very favourable to appearance of 

 Hessian Fly, many observations of it might have been expected if the 

 infestation was still present to any important extent in this country, I 

 only received one report of its presence. This was sent me at the 

 beginning of August, from Barton, near Marlborough, by Mr. D. 

 D. Gibb, for many years a contributor to my Annual Reports, and 

 who has especially helped me by notes of observation of this and other 

 corn pests. 



On August 4th I received a communication from Mr. Gibb, in 

 which, after mentioning that he forwarded me some pieces of Wheat 

 straw, which he considered showed the presence of insect pests to 

 some considerable extent on the Wiltshire Downs, he further re- 

 marked : — 



" My attention was called to part of a large field of Wheat, some 

 fifty-eight acres, which as a whole was a satisfactory crop, say five 

 quarters per acre. But in those parts where the soil was thinnest — near 

 the chalk — the straw was very much broken and twisted over the ground. 

 One of the very first straws examined yesterday, when the cutting was 

 in operation, contained the "flax-seed" of Hessian Fly. On further 

 examination to-day these do not seem to be so numerous over the field 

 as at first expected. Wheat-bulb Fly has done most mischief, unless 

 Hessian Fly attacked very early last autumn close to the root. In 

 pulling, the empty pupa-cases fall out, after which it is difficult, 

 without very careful examination, to distinguish between the two." 



Together with Mr. Gibb's communication, he forwarded me a 

 sample of the Hessian Fly infestation in the chrysalis or pupal state, 

 in which it is commonly observed on straw in summer (see fig. 2, p. 36) ; 

 but it will be noticed that Mr. Gibb also alludes to possibility of attack 

 having occurred to the young autumn Wheat. This sometimes takes 

 place to a destructive extent, but is much less observable than that to 

 the summer straw, and I am not able to recall an instance of this 



D 



