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. 



FlG . 323 ._wings of C 



