F. M. CAMPBELL—THE HESSIAN - FLY. 
187 
dies. By this time the larva is mature and passes into the dormant 
stage, in which it remains until the first days of spring, when, 
after turning into a pupa, it emerges as an imago. From a note in 
the ‘American Naturalist’ (vol. xviii, part 1, p. 195) it would 
appear that many puparia are destroyed by the winter, for the 
writer states that he has often dug up and examined roots during 
that season, and has found the larvae dead and rotten. 
In a country like ours the sowing of wheat is later than in 
America, and the perfect insects of the first, or April or May, 
brood, which breed in autumn, have passed away before the 
blades appear. But in clover fields, if not elsewhere, there is 
young growth from injured and self-sown plants of both wheat 
and barley which offer a brood-place, and Mr. Palmer has found 
the pupae on self-sown barley in October. Further, it is said 
that in 1797, in America, Timothy-grass (Phleum pratense) was 
attacked. But Wagner’s experiences in Fulda in Hesse * alone 
lead us to dismiss any consolation derived from a possible difficulty 
of the pest finding a suitable nidus for its eggs in September and 
October. In March, 1861, he examined a field of young clover 
sown in the autumn of 1859 with wheat, of which there remained 
nothing but the stubble. In this he not only found puparia, but 
also on the same plant empty cases from which the imago had 
emerged. Now, as already stated, the larvae feed on the young 
plants, so that they could not have proceeded from eggs laid during 
the autumn of 1860. He collected some of the puparia and the flies 
hatched out between the 13th of April and the 12th of May. He 
sums up these observations as follows:—viz. that the eggs out of 
which are produced the larvae hybemating on stubble are deposited 
in May, the perfect insects appear the following year in April and 
May, and the metamorphosis of these flies requires one year. This 
is in accordance with Harris,! who, in 1852, stated: “The trans¬ 
formation of some in each brood appears to be retarded beyond the 
usual time, as is found to be the case with many other insects, 
so that the life of these individuals, from the egg to the winged 
state, extends to a year or more in length.” It is clear from the 
above, that the late period of sowing wheat in this country, as 
compared with that in America, does not prevent the propagation 
of the fly. My own experience leads me to think that most of 
the offspring of the first, or spring, brood do not appear as perfect 
insects until the following year. 
The fact, however, that both empty and occupied puparia were 
found on the same plant under the circumstances mentioned by B. 
Wagner may possibly be otherwise explained than by protracted 
development. Nicholas Wagner J discovered that the larvae of one 
* ‘ Untersuchungen liber die neue Getreidegallmucke,’ Balthaser Wagner, 
Fulda, 1861, p. 17. A translation appears in the Appendix to the ‘ Third Beport 
of the U. S. Entomological Commission,’ of which see p. 21 and infra. 
t ‘A Treatise on some of the Insects of New England,’ 2nd ed., p. 455. 
% K. E. von Bae, “ Bericht liber eine neue von Prof. Wagner in Kasan an 
Dipteren beobachtete abweichende Propagationsform,” ‘ Bull. Acad. St. Peters¬ 
burg,’ 1863, p. 239 ; and 4 Zeitschriftwissenschaftliche Zoologie,’ vol. xiii, p. 513. 
