HEX A POD A 213 



KK. Second pair of wings broader, or at least the 

 same size as the first pair. p. 325. . . .Plecoptera 

 JJ. Tarsi four-jointed; wings equal, p. 273. .Isoptera 

 HH. Tarsi consisting of five segments. 



I. Abdomen with setiform, many-]ointed anal filaments. 

 (Certain May-flies), p. 308 Ephemerida 



II. Abdomen without many-jointed anal filaments. 



J. Head prolonged into a trunk-like beak. p. 550.MECOPTERA 

 J J. Head not prolonged into a beak. p. 281.. .Neuroptera 

 GG. Wings with branching veins and comparatively few cross- 

 veins, or veinless. 

 H. Each of the veins of the wing extending along the middle of 



a brown line. p. 338 Embiidina 



HH. Wings not marked with brown lines. 



I. Tarsi two-or three- jointed. 



J. Hind wings smaller than the fore wings. 



K. Cerci present; body less than three millimeters in 



length, p. 270 ZORAPTERA 



KK. Cerci absent; larger insects, p. 331..C0RRODENTIA 



JJ. Posterior wings as large as or larger than the anterior 



ones. (Certain Stone-flies), p. 325 Plecoptera 



II. Tarsi four- or five-jointed. 



J. Abdomen with setiform, many-]ointed anal filaments. 



(Certain May-flies), p. 308 Ephemerida 



JJ. Abdomen without many-jointed anal filaments. 

 K. Prothorax horny. First wings larger than the second, 

 naked or imperceptibly hairy. Second wings without, 

 or with few, unusually simple, veins. Jaws (mandibles) 

 well developed. Palpi small, p. 884. . . . Hvmenoptera 

 KK. Prothorax membranous or, at the most, parchment- 

 like. Second wings as large as or larger than the 

 first, folded lengthwise, with many branching veins. 

 First wings naked or thinly clothed with hair. Jaws 

 (mandibles) inconspicuous. Palpi long. JVIoth-like 



insects, p. 555 Trichoptera 



AA. Wingless or with vestigial or rudimentary wings. 



B. Insects with a distinct head and jointed legs, and capable of locomotion. 

 C. Aquatic insects. 



D. Mouth-parts fitted for piercing and sucking. 



E. Free-swimming nymphs, p. 350 Hemiptera 



EE. Larvae parasitic in sponges (Sisyridae). p. 281 Neuroptera 



DD. Mouth-parts fitted for chewing. 



E. Either somewhat caterpillar-like larvae that live in portable cases or 

 campodeiform larvae that spin nets for catching their food. (Caddice- 



worms). p. 555 Trichoptera 



EE. Neither case-bearing nor net-spinning larvae. 



F. Naiads, that is, immature insects that resemble adults in having 

 the thorax sharply differentiated from the abdomen, and, except in 

 very young individuals, with rudimentary wings. 

 G. Lower lip greatly elongated, jointed, capable of being thrust for- 

 ward, and armed at its extremity with sharp hooks, p. 314.ODONATA 

 GG. Lower lip not capable of being thrust forward. 



H. Usually with filamentous tracheal gills on the ventral side 



of the thorax, p. 325 Plecoptera 



HH. Tracheal gills borne by the first seven abdominal seg- 

 ments, p. 308 Ephemerida 



FF. Larvae, that is, immature forms that do not resemble adults in 

 the form of the body, and in which the developing wings are not 

 visible externally. 

 G. Several segments of the abdomen fiu-nished with prolegs. 



p. 571 Lepidoptera 



GG. With only anal prolegs or with none. 



