662 



AN INTRODUCTION TO ENTOMOLOGY 



Fisr. 8i6. 



measunng-worm. 



SuPERFAMiLY GEOMETROIDEA 

 The Geometrids or the Measuring-worms 



The superfamily Geometroidea is composed of those moths the 

 larvae of which are known as measuring-worms, span-worms, or loopers. 



These larvae are very famiHar objects, 

 attracting attention by their pecuHar 

 manner of locomotion. They progress 

 by a series of looping movements. 

 They first cling to the supporting twig 

 or leaf by their thoracic legs ; then arch 

 up the back v/hile they bring fonvard 

 the hinder part of the body and seize 

 the support, at a point near the thoracic 

 legs, by the prolegs at the caudal end of 

 the body; then, letting loose the thor- 

 acic legs (Fig. 8 1 6), they stretch the body forward, thus making a 

 step; this process is then repeated. 



It was this peculiar man- 

 ner of locomotion that sug- /^^ 

 gested the name of the typic- 

 al genus, Geometra, from 

 the Greek word meaning a 

 land-measurer. 



Correlated with this 

 mode of walking there has 

 been a loss in nearly all 

 members of the family of 

 the first three pairs of pro- 

 legs. 



Frequently measuring- 

 worms when resting cling by 

 their caudal prolegs and 

 hold the body out straight, 

 stiff, and motionless, appear- 

 ing like a twig ; this is doubt- 

 less a protective resem- 

 blance. 



The geometrid larvee are 

 leaf-feeders, and some spe- 

 cies occur in such large num- 

 bers as to be serious pests. 

 The pupae are slender, 

 and some species are green 

 or mottled in this state. 



Fig. 817. — Wings of Caripeta angustiorata. 



The pupa state is passed in a very flimsy cocoon or in a cell in the 

 ground. 



The moths are of vaedmm size, sometimes small, but only rarely 

 very large. Usually the body is slender, and the wings broad and 



