THE ORDERS OF THE HEXAPODA. 51 



D. Front wings leathery at base, and membranous at tip, often over- 

 lapping. Mouth-parts formed for sucking. V. HEMIPTERA. 

 DD. Front wings of same texture throughout. 



E. Front wings horny or leathery, forming veinless wing-covers. 

 (Elytra?) 



F. Abdomen with caudal appendages in the form of movable for- 

 ceps. (Earwigs'.} III. ORTHOPTERA. 

 FF. Abdomen without forcep-like appendages. IX. COLEOPTERA. 

 EE. Front wings leathery or parchment-like, with a network of veins. 

 F. Under wings not folded. Mouth-parts formed for sucking. 



V. HEMIPTERA. 



FF. Under wings folded lengthwise. Mouth-parts formed for biting. 



III. ORTHOPTERA. 

 CC. The two pairs of wings similar, membranous. 



D. Last joint of tarsi bladder-like or hoof-like in form and without claws. 



IV. PHYSOPODA. 

 DD. Last joint of tarsi not bladder-like. 



E. Wings entirely or for the greater part clothed with scales. Mouth- 

 parts formed for sucking. VII. LEPIDOPTERA. 

 EE. Wings naked, transparent, or thinly clothed with hairs. 



F. Mouth-parts arising from the hinder part of the lower surface of 

 the head, and consisting of bristle-like organs enclosed in a jointed 

 sheath. (Homoptera.} V. HEMIPTERA. 



FF. Mouth-parts in normal position. Mandibles not bristle-like. 

 G. Wings net-veined, with many veins and cross-veins. 

 H. Tarsi consisting of less than five segments. 



II. PSEUDONEUROPTERA. 



HH. Tarsi consisting of five segments. 



I. Abdomen with setiform, many-jointed anal filaments. 

 (Certain May-flies?) II. PSEUDONEUROPTERA. 



II. Abdomen without many-jointed anal filaments. 



VI. NEUROPTERA. 



GG. Wings with branching veins and comparatively few cross- 

 veins, or veinless. 

 H. Tarsi two- or three-jointed. 



I. Posterior wings smaller than the anterior. (Psocida.) 



II. PSEUDONEUROPTERA. 



II. Posterior wings as large or larger than the anterior ones. 

 (Certain Stone-flies?) II. PSEUDONEUROPTERA. 



HH. Tarsi four- or five-jointed. 



I. Abdomen with setiform, many-jointed anal filaments. 

 (Certain May- flies?) II. PSEUDONEUROPTERA. 



II. Abdomen without many-jointed anal filaments. 



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

 naked or imperceptibly hairy. Second wings without or 

 with few, usually simple, veins. Jaws (mandibles) well de- 

 veloped. Palpi small. X. HYMENOPTERA. 



