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 1 



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." 



