114 DISEASES OF CROPS. 



of a pink colour at the base, are covered with black hairs. 

 The halteres are of a pale red colour. The female insect is 

 about one-third longer than the male, and has a yellowish- 

 brown abdomen containing a number of spots on each of 

 the eight segments. The legs of both sexes are of a pink 

 colour ; but they are of a darker shade in the female. 



There are generally two broods of this insect in each 

 season. On the authority of Dr. 0. V. Riley, it has been 

 stated that the Hessian fly " is very injurious only under 

 conditions where two annual generations are pretty uni- 

 formly produced ; and he is satisfied that in England, as 

 a rule, only one generation will be produced." Mr. J. E. 

 Mason, of Alford (who reported the discovery of the pest 

 in Lincolnshire during the season of 1889), wrote the 

 author as follows : " As regards the amount of damage, 

 I have come to the conclusion that in our cotmtry it is 

 not at all likely to be serious among the wheat, but that 

 it may be very extensive in the barley crop." 



Fortunately for British agriculture there are certain 

 parasites of Cecidomyia destructor which accompany it 

 to this country. Amongst these are the following : 

 Euryscapus saltator, Platygaster minutus, Eupelmus 

 karschii, Tetrastichus Eileyi, Seiniotellus nigripes, and 

 Merisus intermedius. They are all small four-winged 

 flies, belonging to the Hymenoptera, which lay their 

 eggs in the larva and pupae of C. destructor. The 

 parasites mentioned infest the Hessian fly in Russia, and 

 therefore must have been introduced into England (along 

 with their host) upon imported Russian wheat. They are 

 quite distinct species from those found in America (Linde- 

 man's Die Pteromalinen der Hessenfliege, p. 15).i 



'For further information, see Eiley's Parasites of the Hessian 

 Fly, and Insect Life, vol. i. p. 132 ; Ormerod's The Hessian Fly in 



