618 
DIPTERA. 
I 
pup86 within the onions, and come out as flies a fortnight 
afterwards. 
We have a kind of fly corresponding almost exactly with 
the description of the onion-fly. This strengthens my belief 
that our onions suffer from the depredations of the maggots 
of this or of a similar insect. The fly to which I allude is 
often found on windows in the spring. It is ash-colored, 
with black hairs sparingly scattered on its body. It has a 
rust-colored forked spot on the top of its head, and three 
rust-red lines on the thorax; and the wings are tinged with 
yellow near the shoulders. It measures one fourth of an 
inch in leno;th. It is stated that there are two or three 
generations of the European onion-flies during the summer, 
and that the late broods pass the Avinter in the pupa state, 
and are ready to burst forth at the first warmth of the fol¬ 
lowing spring. It is stated that the onion crop may be pre¬ 
served from the attacks of this fly, by sowing the seed on 
ground upon Avhich a quantity of straw has been previously 
burnt. 
The peculiar disease that has affected potatoes within the 
last ten years has been attributed, by many persons, to the 
depredations of insects. In the course of this Avork, several 
of these insects have been described. Another is noAV to be 
added to them, as Avill be seen by the folloAving extract from 
a letter, receded from a correspondent in July, 1851. “ A 
neAv potato-rot theory has recently appeared in Brattlebor- 
ough, Vermont. The mischief is referred to a fly, of AA^hich 
an authentic specimen is enclosed. It is said that the species 
first appeared simultaneously Avith the potato-rot; and the 
flies are accused of hoA^ering about the manure, and deposit¬ 
ing their eggs, so that the larvae infect the potatoes.” The 
specimen proved to be a common dung-fly, Avhich may be 
found in abundance upon manure Avhen carted into the field 
in the spring. The male is easily distinguished from other 
flies by its yelloAV and very hairy hind body and legs, and 
by its long and narroAv Avings. It is about half as large as a 
