470 AN TNTRODUCTION TO ENTOMOLOGY 



CC. Antennae arising at the side of the head between the base of the mandi- 

 bles and the eyes. 

 D. Beetles of a round convex form in which the scutellum is entirely 



concealed, p. 481 Omophronid^ 



DD. Not such beetles, p. 478 Carabid^ 



BB. Antennae ten- jointed; hind coxas fixed and greatly expanded so as to 

 conceal the basal half of the hind femora and from three to six of the ab- 

 dominal segments; habits aquatic, p. 481 Haliplid^ 



AA. Metasternum either with a very short antecoxal piece, which is separated 

 by an indistinct suture and which is not prolonged posteriorly between 

 the coxae, or without an antecoxal piece. 

 B. Metasternum with a very short antecoxal piece, p. 481 .Amphizoid^ 

 BB. Metasternum without an antecoxal piece. 

 C. Legs fitted for swimming. 



D. With only two eyes. p. 482 Dytiscid^ 



DD. With four eyes, two above and two below, p. 484. .Gyrinid^ 

 CC. Legs fitted for walking, p. 508 RHYSODiDiE* 



TABLE III.— THE FAMILIES OF THE BRACHELYTRA 



A. Elytra short, leaving the greater part of the abdomen exposed; the suture 

 between the elytra when closed straight; wings present, and when not in use 

 folded beneath the short elytra; the dorsal part of the abdominal segments en- 

 tirely horny. 

 B. Abdomen flexible, and with seven or eight segments visible below, p. 488. 



Staphylinid^ 



BB. Abdomen not flexible, and with only five or six ventral segments visible. 



C. Antennas with less than six joints, p. 490 Clavigerid^ 



CC. Antennae eleven-jointed, rarely ten-jointed, p. 489..PSELAPHID.E 

 AA. Elytra usually long, covering the greater part of the abdomen; when 

 short the wings are wanting, or, if present, may or may not be folded under 

 the short elytra when at rest; the dorsal part of the abdominal segments 

 partly membranous. 

 B. Hind tarsi five-jointed. 



C. Antennas elbowed, and clavate. p. 490 Histerid^ 



CC. Antennae rarely elbowed, and then not clavate. 

 D. Abdomen with not more than five ventral segments. 



E. Antennae capitate, the last three segments forming an abrupt club. 



p. 490 SPH^RITID^t 



EE. Antennae but slightly clavate if at all. p. 490.. . .Scaphidiid^ 

 DD. Abdomen with six or more ventral segments. 



E. Anterior coxae flat. p. 486 Platypsyllid^ 



EE. Anterior coxs either globular or conical. 



F. Anterior coxae globular, p. 487 Leptinid^ 



FF. Anterior coxas conical. 



G. Posterior coxae widely separated. 



H. Eyes wanting or inconspicuous, p. 487 Silphid^ 



HH. With well-developed eyes. 



I. Elytra covering the abdomen, p. 488 . . . ScYDM^ENiDiE 



II. Elytra not covering the entire abdomen, p. 490 



SCAPHIDIID^ 



GG. Posterior coxae approximate. 



H. Posterior .coxae laminate, p. 488 Clambid^ 



HH. Posterior cox® not laminate. 



*The Rhysodidas is a very aberrant family, and its affinities have been much 

 discussed. The form of the ventral part of the first abdominal segment is similar 

 to that characteristic of the Adephaga; hence, according to Table I, this family 

 should be placed in this suborder. But other characters led Leconte and Horn 

 ('83) to place it in the Clavicornia, in which view they are followed by recent 

 writers. 



fSee also p. 508, the Nitidulidas of the series Clavicornia. 



