670 



AN INTRODUCTION TO ENTOMOLOGY 



species (Fig. 829). Although the wings are yellowish white in color 

 they are almost transparent. On the fore wings there are two trans- 

 verse rows of pale gray spots, and a single spot near the outer margin 

 between veins M^ and Cui. (This spot was indistinct in the specimen 

 figured.) The moth is commion in midsiunmer. The larva feeds on 

 violet. 



Subfamily GEOMETRIN^E 



Nearly all of the members of this subfamly can be easily recognized 

 as such by the fact that vein M2 of the hind wings is wanting, being 

 represented merely by a fold. 



This is by far the largest of the subfamilies of the Geometridae; 

 it includes more than 500 North American species; these represent 

 124 genera. The following are some of the more common species. 



The currant span-worm, Cymatophora rihedria. — There are several 

 species of insects that are popularly known as currant-worms. The 

 most common of these are larvae of saw-fiies, which can be easily 

 recognized by the large number of prolegs with which the abdomen 



Fig. 830. — Cymatophora ribearia. 



Fig. 831. — Cingilia catenaria. 



is furnished. In addition to the saw-fiies there is a yellow looper 

 spotted with black, which often appears in such great numbers on 

 currant and gooseberry bushes as to suddenly strip them of their 

 foliage. 



This larva has been named the currant or gooseberry span-worm. 

 When full-grown it measures about 2 5 mm. in length, and is of a bright 

 yellow color, with white lines on the sides and with numerous black 

 spots and round dots. It has only four prolegs. There is only one 

 generation a year; the larva matures in May or June; the pupa state 

 lasts about a "fortnight ; the moth flies during the summer months and 

 oviposits on the twigs of the plants; and the eggs remain unhatched 

 till the following spring. The moth (Fig. 830) is pale yellow, with the 

 wings marked by irregular dusky spots, which sometimes form one 

 or two indefinite bands across them. 



The chain-dotted geometer, CingUia catenaria. — This moth has 

 snow-white wings marked with zigzag lines and with dots of black as 

 shown in Figure 83 1 . The head is ochreous-yellow in front ; and the 

 thorax is yellowish at the base of the patagia. The moth flies during 



