LECTURE IX. 
115 
in manner of life and place of residence, some 
liv^ing on putrid animal substances, some on the 
smaller insects; and some are of an aquatic na- 
ture. Some Flies, as a species greatly allied to 
the common Window-Fly for instance, are ovi- 
viviparous, producing living Maggots, which have 
themselves been first hatched internally. 
The Common Gnat belongs to a genus called 
Culejc, and is sufficiently known to supersede the 
necessity of particular description. It deposits 
its eggs in groupes on the surface of stagnant wa- 
ters, and the young during their larva state are of a 
very peculiar appearance. When changed into the 
chrysalis state they are still loco-motive, and when 
ready for the production of the perfect Insect spring 
to the surface of the water, and give birth to it. 
In the genus called CEstrus or Gad-Fly the 
eggs are laid by the parent insect in the skin of 
the backs of Cattle, in one species ; in others in 
the nostrils and other parts of Deer and Sheep : 
the larves, when arrived at their full size, creep 
out, and retiring beneath the surface of the gra^s 
or under any convenient body, change into a 
chrysalis, from which in a certain space springs 
the animal in its ultimate form. 
