which attack cereal crops. 615 
minute, being only about one line in length, and about 
24 lines in the expanse of the wings. ‘They are black, 
slightly glossy, and with a very little brassy tinge; the 
halteres are whitish, the legs entirely black, the wings 
colourless, or but very slightly ashy coloured, with dark 
slender veins. The forehead is elevated and rounded, 
the face slightly emarginate in its profile in front of the 
eyes, for the reception of the antenne, which have the 
principal joint short and semi-rounded, with a slender 
and slightly setose dorsal bristle or terminal joint. The 
mouth is a beautiful microscopical object, with two 
clavate, setose palpi, a strong, short, pointed, horny 
tongue, and a large fleshy lip notched in the middle of 
its terminal margin so as to form two lobes, each of 
which is traversed by three fine curved transversely 
striated muscles. 
This species, although closely allied to Oscinis vastator, 
Curtis (‘Farm Insects,’ p. 239, pl. H, fig. 117), differs 
in the colour of the legs, which in the latter insect have 
the base and tips of the four anterior tibize ferruginous, 
the base of the first jot in all the tarsi of the same 
colour, whilst the legs are uniformly black in Mr. Yonge’s 
insects. From this slight difference I was led to infer 
that the habits of the latter were identical with those of 
My. Curtis’s insect, and that its larva fed on the stems of 
the oats. This supposition was, however, contradicted 
by the fact that the flies had only made their appearance 
after the grain had been threshed out in the field and the 
oats stored in the loft. At all events, the mischief, 
whatever it might have been (and Mr. Yonge says that 
the grain did not appear to be injured), had been done, 
and no more damage was to be apprehended from the 
flies, which were making their appearance in such 
incredible numbers. Finding, however, in the bottle 
which contained the flies, two or three grains of the oats, 
I opened them carefully, and found, within the enveloping 
scales of one of the grains, the remains of an Aphis, 
and within another (in which the grain itself had dis- 
appeared) there remained only the shrivelled feathery 
styles of the ovary, above which was the empty scaly 
elongate-ovate covering of the puparium of one of the 
little flies, which had left the grain and joined its com- 
panions in their escape from the loft. Thus the cause 
of the appearance of these flies after the grain was 
housed was accounted for, and the species was proved to 
