586 DIPTERA. 



to feed oflF tlie crop late in the autumn, and it lias also 

 been recommended to turn them into the fields again in 

 the spring, in order to retard the growth of the plant till 

 after the fly has disappeared.* Too much cannot be said 

 in favor of a iudicious management of the soil, feedino- 

 off the crop by cattle in the autumn, and burning the 

 stubble after harvest ; a proper and general attention to 

 ■which will materially lessen the evils arising from the 

 depredations of this noxious insect. 



Fortunately our efforts will be aided by a host of j^ara- 

 sitical insects, which are found to prey upon tlie eggs, the 

 larvae, and the pupae of the Hessian fly. Mr. Herrick 

 states, f that, in this part of the country, a very large pro- 

 portion, probably more than nine tenths, of every genera- 

 tion of this fly is thus destroyed. One of these parasites 

 was made known by Mr. Say, in the first volume of the 

 " Journal of the Academy of Natural Sciences of Phila- 

 delphia " ; and the interesting discovery of three more 

 kinds is due to the exertions of ]\Ir. Herrick. They are 

 all minute Hymenopterous insects, similar in their habits 

 to the true Ichneumon-flies. 



The chief parasite of the pupa is the Cerapliron destructor \ 

 of Say, a shining black four-winged fly, about one tenth 

 of an inch in length. This has often been mistaken for 

 the Hessian fly, from being seen in wheat-fields, in vast 

 numbers, and from its being found to come out of the dried 

 larva-skin of that fly. In the month of June, when the 

 maggot of the Hessian fly has taken the form of a flax-seed, 

 the Ccraphron pierces it, through the sheath of the leaf, 

 and lays an egg in the minute hole thus made. From this 



* Cultiviitor, Vol. IV. p. 110, ami Vol. V. p. 49. 



t American Journal of Science, Vol. XLI. p. 156. 



\ It is evident, from Air. Say's description, and from Mr. Lesueur's figures, that 

 this insect is not a Ceraj^hron. Neither does it belong to the genus Eurytuma, to 

 which I formerly referred it. It certaiidy comes very near to Pieromalus, as sug- 

 gested by Mr. Westwood; but I ajjprehend that it should be placed in the genus 

 Rhaphhelus of Walker, or Storthygocerus of Ratzeburg. 



