626 



THE STUD Y 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 

 graas 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 ApJiidius (A-phid^i-us). 

 The members of this genus are minute creat- 

 ures which infest piant-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 w^hich the insects 

 were when they died. From each one there 

 emerges in due time an Aphidhis, 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- 

 louse in which to oviposit she stands with her head towards 

 it, and bending her abdomen under her thorax between her 

 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 



I'^iG. 753- 



FiG. 754. 



