306 ELEMENTARY ENTOMOLOGY 



CC. Ventral spring attached to antepenultimate abdominal segment. 



PODURIDAE 

 BB. Ventral spring absent APHORURIDAE 



THE EPHEMERIDA 



This order includes only a single family, the members of which have deli- 

 cate membranous wings with a fine network of veins. The fore-wings are 

 large, and the hind-wings much smaller or wanting. Mouth-parts rudimentary. 

 May-flies. (Page 95) EPHEMERIDAE 



KEY TO THE FAMILIES OF ODONATA* 



A. Front and hind wings similar in outline, distinctly narrow at base, held 

 vertically over the back when at rest. Damsel-flies. (Page 98) Sub- 

 order ZYGOPTERA 



B. Wings with not less than five antecubital cross veins. CALOPTERYGIDAE 

 BB. Wings with not more than three, usually two, antecubital cross veins. 



AGRIONIDAE 



A A. Front and hind wings dissimilar, the hind- wings being much wider at the 

 base ; wings held horizontally when at rest. Dragon-flies. (Page 98) 



Suborder ANISOPTERA 

 B. Antecubital cross veins of first and second rows usually meeting each 



other LIBELLULIDAE 



BB . Antecubital cross veins of first and second rows not meeting each other. 

 C. Eyes meeting above in median line of head ; abdomen with lateral 



ridges AESCHNIDAE 



CC. Eyes separate, or nearly so ; abdomen without lateral ridges. 

 D. Eyes touching at a single point, or barely apart. 



CORDULEGASTERIDAE 



DD. Eyes distinctly separated GOMPHIDAE 



THE PLECOPTERA 



This order includes only a single family, having four membranous wings, 

 the hind-wings being folded plaitlike under the fore-wings. The mouth-parts 

 are biting, but slightly developed. Stone-flies. (Page 97) . . . PERLIDAE 



KEY TO THE FAMILIES OF NEUROPTERA 



A. Hind-wings broad at base, the inner margin folded in plaits. Dobsons. 



(Page 90) SIALIDAE 



A A. Hind-wings narrow at base, not folded in plaits. 

 B. Prothorax greatly prolonged into necklike stalk. 



1 Revised from Kellogg's "American Insects." 



