APPENDIX 529 



' attaining a diameter equal to one fourth the width 

 of the abdomen (11) Dytiscus 



Front margin of the eye more or less deeply notched, 

 by the intruding margin of the front of the head; 

 stigmata nearly uniform in diameter 16 



16. A linear group of minute setae present upon the pos- 



tero-external angle of the hind femur (fig. 285c) . . 17 



No such linear group of setae present 21 



17. Claws of the hind tarsus equal, and joints sim])le. . 18 

 Hind tarsus with its claws unequal, and its joints 



produced posteriorly in overlapping lobes (16) 



Ilybius 



18. Palpi with the terminal joint dilated, that of the 



labial palpi sub-quadrate (Calif.) (i) Hydrotnipes 

 Palpi with the terminal joint not conspicuously di- 

 lated 19 



19. Wing of the metasternum wedge-shaped 20 



Wing of the metasternum linear, and dcflexed around 



the front border of the external lamina of the hind 

 coxa (8) Ilyhiosoma 



20. Coxal lines very deep and nearly straight (Calif.) (i) 



.4 gab inns 

 Coxal lines fine and sinuous (48) Agabus 



21. Last joint of palpi emarginatc at tip (3) Coptotomus 

 Last joint of palpi rounded or truncate at tip 22 



22. Prosternum with a deep median longitudinal 



groove (i) E. U. S Mains 



Prosternum not grooved 23 



23. Claws of the hind tarsi equal, movable 24 



Claws of the hind tarsi unequal, the outer one fixed 25 



24. The coxal border very broad (i) \gabctcs 



The coxal border very narrow (2) Copelatiis 



25. Upper surface of the body conspicuously reticulate 



(2) Scutoptcrns 



