LEPIDOPTERA. 
271 
these worms from the sharp-eyed birds. If so, we should 
have been still more interested in them ; and we should have 
been even more so could some one have told us of the 
transformation of these loopers first into pupae and then 
into beautiful moths. But in those days comparatively few 
people thought it worth while to study insects. 
The larvae of Geometrids have as a rule only the last two 
pairs of prolegs well developed ; and hence, as the middle 
part of the body is not supported, they are unable to walk in 
the way that other caterpillars walk. It is probable, however, 
that the loss of the first three pairs of prolegs is the result of the 
looping gait rather than the cause of it. That is to say, the 
ancient Geometrid lar¬ 
vae acquired the habit 
of looping, after which 
the prolegs under the 
middle of the body, 
being unnecessary and 
not used, dwindled 
away in succeeding 
generations. In the 
case of a few members 
of this family three or 
even four pairs of pro¬ 
legs have been re¬ 
tained. 
The Geometrid lar¬ 
vae are mostly leaf-eat¬ 
ing, and some species, 
as the Canker-worms, 
occur in such large 
numbers as to be 
serious pests. 
The pupae are slender, and some species are green or 
mottled in color in this state. The pupa state is passed in a 
very flimsy cocoon or in a cell in the ground. 
Fig. 322.—Wings of Caripeta angustiorata . 
