FIELD BOOK OF INSECTS, 



5. Body flat above; top of head free from pronotum; 

 front tarsi flattened, I -jointed, without claws, edges 

 fringed; beak with not more than 2 joints, hidden 



CORIXID,<E (p. 99). 



Body convex above and pronotum overlapping the 

 head; front tarsi normal, 2-clawed; beak 3- or 4-jointed 



NOTONECTID^E (p. lOO). 



6. Membrane with veins 7. 



Membrane without veins. NAUCORID^E. They re- 

 semble Gelastocoridae (3) but do not have prominent eyes, 

 and crawl about on submerged plants. Pelocoris is our 

 only genus. P. femoratus is about .4 in. long; pronotum 

 shiny yellow or light brow 7 n, marked with numerous dark 

 spots; front wings dark brown with a light shoulder-area. 

 Ambry sus occurs in the West. 



7. Apical appendages of abdomen long and slender, not 

 retractile ; hind legs formed for walking . . . NEPID^E (p. 100). 



Such.. appendages short, flat, and retractile; hind legs 

 flattened for swimming BELOSTOMID/E (p. 99). 



8. Head shorter than thorax, including scutellum 9. 



Head as long as entire thorax; body and legs slen- 

 der HYDROMETRID^E (p. 104). 



9. Last tarsal joint divided, claws back of tip; front 

 wings, if present, of rather uniform texture throughout. . 10. 



Last tarsal joint not divided, claws at tip 1 1. 



10. Middle and hind legs very long, close together 

 and distant from the front pair; beak 4-jointed but the 

 first joint short GERRID.E (p. 103). 



Middle and hind legs not very long, more equally 

 spaced; beak 3-jointed VELIID.E (p. 103). 



11. Antennae 5-jointed 12. 



Antennae 4-jointed (Do not count either the tubercle 



which bears the antennae or the minute intermediate 

 segments which are sometimes present) 13. 



12. First and second antennal segments thicker than 

 the others; minute bugs living on surface of water. 

 HEBRID.E. Plebrus, our only genus. 



First antennal segment thick, second slender; scu- 

 tellum rather large 27. 



13. Prosternum with a median, longitudinal, striated 

 or granulated, stridulatory groove visible in front of front 



96 



