440 
The Progress of ihe Hessian Fly. 
two pupa-cases found in the joint of one stem of a plant, and no 
indications that any other parts of it have been attacked. Yet 
the stem itself is shortened and bent down, and its ear compara- 
tively empty, and the whole plant is less vigorous than those 
near and uninfested. This was more plainly shown this season 
upon barley-plants than upon wheat-plants, though in the 
latter there was a clear difference upon close observation. Dr.- 
Lindeman considers that the simple exhaustion of sap and the 
local irritation set up by the larvae are not sufficient by them- 
selves to occasion the mischief, and suggests that the larva 
secretes poisonous matter which permeates the whole system 
of the infested plant and injuriously affects it. In this view he 
is supported by Dr. Cohn. 
Concerning the pupa-cases, or puparia, in this country, nothing 
more is known than has been published by Miss Ormerod, 
and by the Agricultural Department of the Privy Council. 
Their development in confinement, that is, in artificial condi- 
tions, is most uncertain and irregular, and cannot be accepted as 
positive proof of habit in a natural state. In some instances 
the fly in confinement came from the pupa-case in the late 
autumn in about 15 days. In others the change to the fly 
form did not take place until the spring ; the pupa remained 
unchanged throughout the winter, though the temperature was 
maintained at an equable autumn and spring point. That some 
of the pupae of the spring generation do not change in the 
autumn while in a natural state, is quite clear, because the 
pupa-cases were found last winter upon self-sown corn-plants, 
and those carried with corn in the straw to ricks and barns 
remained perforce in a state of hibernation. This, however, 
does not affect their vitality, as such pupa-cases taken from tail 
corn in February produced flies in confinement. Obviously it 
is difficult, or, at least, it requires patient watching to witness 
the emerging of the flies from the pupa-cases in the fieWs, and 
no accurate information is yet available upon this ] oint. It is 
hoped that in time, this and other results of continuous obser- 
vation may be forthcoming. 
There is nothing definitely settled as to the number of the 
generationsof the Hessian Fly in England, though it is generally 
accepted that there are two, as in America ; namely, that which 
comes forth in the autumn and infests the " fall " wheat, and 
that which appears in the spring and attacks both wheat- a«d 
barley-plants. Dr. Lindeman is of opinion that there are 
three generations in Mid-Russia, and even four in a district of 
Southern Russia.* It is assumed, however, that there is not a 
• Op. cit. 
