206 INSECTS 
wormlike in form and are usually provided with from 8 to . 
16 legs. They are of various colors, and some are covered i 
with thick, short hair, while others are perfectly smooth. 
All caterpillars are great eaters and are destructive to vege- © 
tation. Some of our worst insect pests, such as cut worms, 
army worms, and measuring worms, are caterpillars. The 
adult moths and butterflies, however, are harmless. They 
can partake of no nourishment but a little nectar which they 
suck from flowers. 
There are more than 6000 species of moths and butterflies 
known to occur in America north of our Mexican boundary. 
Flies and Mosquitoes. This class of insects is easily 
distinguished by the fact that they have only two wings. 
The mouth parts are formed ' 
for sucking. There are said to 
be about 8000 species of flies 
in North America, but as the 
house fly is the commonest and 
most important, we shall con- 
Lire History or tHE House Fry fine our attention to that. 
a, Adult; 6, Eggs; c, The larvaor House flies lay their eggs in 
eS ac ad all kinds of filth, most com- 
monly horse manure, where the larva and pupa stages are 
to be spent. The eggs hatch in 24 hours or less. The larve, 
called maggots, are yellowish white in color and are footless. 
In a week’s time they enter the pupa state, and in less than 
another week the full-grown flies appear. The females be- 
gin laying eggs in from nine to fourteen days after this. 
The length of all these periods varies with the temperature 
and other conditions, but generally the time from egg pro- 
duction by one generation to egg production by the next 
generation ranges from 16 to 25 days, and there may be 
| 
| 
