626 
THE STUDY OF INSECTS. 
tiful objects, resembling in miniature those of the silkworm. 
The adult parasite in emerging from its cocoon cuts a neat 
little lid at its upper end. These parasites belong to the 
genus Microgaster (Mic-ro-gas'ter). Bunches of white or 
yellow cocoons of Microgaster are often found attached to 
grass or other plants instead of to the back of the caterpillar 
which the larvae have destroyed (Fig. 753). 
Perhaps the most interesting of the com¬ 
mon forms belonging to this family are those 
belonging to the genus Aphidius (A-phid'i-us). 
The members of this genus are minute creat- 
ures which infest plant-lice. If colonies of 
Aphides be examined, the dried bodies of 
dead ones may be found in which the abdo¬ 
men is more or less spherical, being greatly 
distended. These bodies remain clinging to 
the leaves in the position in which the insects 
were when they died. From each one there 
emerges in due time an Aphidius. The para¬ 
site in emerging cuts a very 
regular circular lid in the dor¬ 
sal wall of the abdomen of its host (Fig. 754). 
We have watched with much interest these 
little Braconids ovipositing in the bodies of 
plant-lice. When one has selected a plant- Fig. 754. 
louse in which to oviposit she stands with her head towards 
it, and bending her abdomen under her thorax between he* 
legs she darts her ovipositor forward into the body of the 
Aphis. The species of this genus do not construct co¬ 
coons, but undergo their metamorphoses within the dried 
skins of the plant-lice. 
Family Evaniid^ (Ev-a-ni'i-dae). 
The Ensign-flies . 
This is a small family, comprising insects of very peculiar 
structure. They can be easily distinguished by the fact 
