126 THE STUDY OF INSECTS. 



BB. Hind~tarsi with two claws. 



C. Caudal end of the abdomen furnished with a respiratory tube 

 composed of a pair of grooved, thread-like organs, p. 130. 



Nepid^e. 

 CC. Caudal end of abdomen without respiratory tube. 



D. Legs flattened, fitted for swimming; caudal end of the ab- 

 domen furnished with a pair of strap-like appendages (these 

 appendages are retractile and are frequently withdrawn from 



sight), p. 131 Belostomid^e. 



DD. Legs fitted for walking; abdomen without strap-like 

 caudal appendages. 



E. Without ocelli, p. 133 Naucorid^e. 



EE. Ocelli present, p. 133 Galgulid^e. 



AA. Antennae at least as long as the head, usually free, rarely (Fky- 

 matidce) fitting in a groove under the lateral margin of the pro- 

 notum. 

 B. Body linear ; head as long as the three thoracic segments. 



p. 136 LlMNOBATIDiE. 



BB. Body of various forms, but, when linear, with the head shorter 

 than the thorax. 



C. Last segment of the tarsi more or less split, and with the 

 claws inserted before the apex. 



D. Body usually elongated; prothorax narrow; beak four- 

 jointed; second and third pairs of legs extremely long and 



slender, p. 135 Hydrobatid^:. 



DD. Body usually stout, oval, and broadest across the protho- 

 rax; beak three-jointed; legs not extremely long. p. 134. 



Veliid^e. 

 CC. Last segment of the tarsi entire, and with the claws inserted 

 at the apex. 

 D. Antennae four-jointed.* 



E. Wing-covers resembling network, and very rarely (Piesma 

 with any distinction between the corium and the mem- 

 brane, p. 139 TlNGITIDiE. 



EE. Wing-covers of various forms or absent, but not of the 

 form presented by the Tingitidae. See Fig. 165. 

 F. Beak three-jointed. 



*In certain families there are minute intermediate segments between the 

 principal segments of the antennae. For the purposes of this table these 

 intermediate segments are not counted. 



