586 
DIPTERA. 
to feed off the crop late in the autumn, and it has also 
been recommended to turn them into the fields ao-ain 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 judicious management of the soil, feeding 
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 para¬ 
sitical insects, which are found to prey upon the eggs, the 
larvae, and tlie pupae of the Hessian fly. Mr. Herrick 
states,! 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 tlie 
Journal of the Academy of Natural Sciences of Phila¬ 
delphia ” ; and the interesting discovery of three more 
kinds is due to the exertions of Mr. 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 
O 
the. Hessian fly, from being seen in wheat-fields, in vast 
numbers, and from its beino; 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 Cerapliron pierces it, through the sheath of the leaf, 
and lays an egg in the minute hole thus made. From this 
* Cultivator, Yol. IV. p. 110, and Yol. Y. p. 49. 
t American Journal of Science, Yol. XLI. p. 156. 
t It is evident, from Mr. Say’s description, and from Mr. Lesueur’s figures, that 
this insect is not a Cerajjihron. Neither does it belong to the genus Eurytoma, to 
which I formerly referred it. It certainly comes very near to Pteromaliis, as sug¬ 
gested by Mr. Westwood; but I apprehend that it should be placed in the genus 
WwpMtelus of Walker, or Storihyyocerus of Ratzeburg. 
I 
