A Short Sketch of the Ichneumons. 143 
the evening, so that if the gas is lit in any room, and the window 
left open, numbers of these ichneumons will be attracted by the 
light, and will fly to the lamp and scorch themselves. 
The fortunate possessor of a microscope may take an 
appropriate revenge for this, at times, rather unwelcome intrusion, 
by mounting the head of this insect, as a transparent object, in 
balsam without pressure. If the mounting has been properly done, 
and the specimen be examined under an inch objective, the various 
organs will be beautifully seen in succession, by gradually focus- 
sing down from the upper to the lower parts of the head. First, 
we see the bases of the antennz and the three simple eyes; next, 
the compound eyes and the powerful mandibles come into view. 
Still screwing down the coarse adjustment, the mandibles become 
obliterated, and are replaced by the less horny maxille or lower 
jaws, with their long palpi attached ; lastly, the labium and its 
labial palpi, with the delicate tongue or lingua in the centre, are 
seen when the bottom of the specimen is brought into focus. 
We shall conclude these remarks with a brief sketch of the 
methods of oviposition and life-history of the various Braconites 
and Ichneumonites. 
A few kinds attach their eggs to the external surface of the 
body of the caterpillar, and the larvee live outside, but this is not 
very usual. There are two other methods. One of these is to 
insert the egg in a puncture made in the skin of the caterpillar; this 
method is very generally adopted. In the other, the ichneumon 
attacks the eggs instead of the larvze of its victim, so that when 
these hatch and develop, the eggs of ichneumon also hatch inside 
them, and their larvee begin to attack the caterpillar at once. 
The ichneumon larvee feed only on the fatty parts of their host, 
leaving the vital parts untouched. In some cases they emerge 
from the body of the caterpillar, preparatory to transforming into 
the pupa state, and their cocoons may be seen hanging, in con- 
siderable numbers, attached to the body of their former host, which 
continues to live. In other cases they remain where they are 
until the caterpillar containing them has passed into the 
chrysalis state, and, instead of a moth or butterfly emerging 
from the pupa case, one or more ichneumons appear in its place. 
A very nearly full-grown ichneumon larva has been known to 
emerge from the captured imago of a moth. 
When the ichneumons have attained the perfect state, they 
occasionally feed on the juices of flowers. 
There is scarcely a single insect which has not its own special 
ichneumon, while some species, not content with destroying 
one kind of insect, attack several. Even those caterpillars which 
are provided with urticating hairs do not derive any immunity 
from the attacks of ichneumons, by this protection. Nor are 
