affecting the Corn- Crops. 
141 
Tipula tritici and its parasite. In 1797 Mr. Kirby sa\'s, in a 
letter to Mr. Marshani, he could scarcely pass through a wheat- 
field in which some florets of every ear he examined were not 
inhabited by the larva? of the Tipula, but very few pupae, not one 
in fifty. About the beginning of September he bred one of the 
flies, and describes it as well as the parasitic Idineumon. He 
searched in vain for more flies in the corn-fields and barns soon 
after, but could find none, from which he concluded they did not 
hatch in general in a natural way until the spring, so as the female 
might be " in readiness to deposit its eggs in the wheat, when it 
has made so much progress in growth that the larva may be 
hatched about the lime of its going into blossom ; and I am con- 
firmed in this opinion by another circumstance. A few days since 
(the fourth week in September) with a fine needle 1 carefully took 
oflF the thin membrane from two of the pupae which I had reserved, 
that I might see how near they were to a change of state; but 
instead of discovering the lineaments of the future fly, the insect 
was still in the form of the larva : so that probably the pupa is not 
usually complete until the spring, and the insect incloses itself in 
a thin membrane to protect itself from the cold of the winter." 
Mr. Kirby adds, " It may be objected that this was probably the 
larva of the Ichneumon, which had devoured that of the Tipula. 
To this I reply, that it was in colour, form, and in every respect 
so exactly similar to the latter that it could be no other." 
" I have seen," continues the same learned naturalist, " more 
than once, seven or eight florets in an ear inhabited by the larvae, 
and sometimes so many as thirty in a single floret, seldom less 
than eight or nine, and yet I have scarcely ever found more than 
one pupa in an ear, and had to examine several to meet with that. 
\Miat then becomes of the remainder of the larvse ? Are they 
destroyed by that of the Ichneumon'? or do they become the prey 
of some other insect, or do they fall to the ground when they 
assume the pnpa, and remain there until the following spring ? 
To give a positive answer to any one of these queries I shall not 
pretend ; I will only relate circumstances, and point out from 
them what appears to me to be most probable. I'he pupaj that I 
have observed have generally been somewhat attached to the grain, 
and, what is worthy of notice, I never found them within those 
florets where the larvae had taken up their residence ; they seem 
invariably to choose for their habitation, in their intermediate state, 
one where the grain is uninjured, to which they may attach them- 
selves (fig. 16). A question here arises, how they contrive to get 
from one floret to another, having no feet ? But as I have never 
seen them do this, I will not attempt to conjecture how they do it. 
In the field above mentioned, I took up many roots of stubble, 
with a large lump of earth round them, to see if I could discover 
