THE WATER SCAVENGER BEETLES. 247 



Subseries D. TRIUERA CLAVICORNIA. 



The members of this group have the tarsi all 3-jointed and the 

 ventral segments free. They live either in fungi or feed upon plant 

 lice. The following families of the suhseries are represented in the 

 State : 



KEY TO INDIANA FAMILIES OF TRIMEKA CLAVICORNIA. 



'/. Wings fringed with long hairs; abdomen not prolonged and with (' or 7 



ventral segments; antenna? with the basal and apical joints thicker 



than the middle ones, the latter with whorls of long hairs; length 



less than 1' mm. Family XII. TRICHOPTERYGIIKE. p. 4sr>. 



r/(/. Wings not fringed. 



b. Tarsi with second .joint dilated; third joint consisting really of two 

 joints, the small true third joint being inserted at the base of the 

 last joint. 



c. Tarsal claws dilated or toothed at base; h'rst ventral segment with 

 coxal lines: form usually rounded and convex; bead nearly con- 

 cealed by the thorax; last joint of maxillary palpi usually 

 hatchet-shaped; length less than S.."i mm. 



Family XVI. CocriXKLLiu.-E. p. TOG. 



re. Tarsal claws simple; first ventral without coxal lines; form oblong 

 or oval, rarely globose; last joint of maxillary palpi oval or tri- 

 angular; length less than <!..""> mm. 



Family XVII. EMDOM vciun.E. p. .">:!:>. 

 l>l>. Tarsi with second joint not dilated and without a pseudo fourth 



joint. 



<L Elytra entire; ventral segments nearly equal: front coxal cavities 

 rounded, not prolonged mi the outer side; length less than ."> mm. 



Family XXVII. LATHUIIMID.E. p. (!.">!. 



(hi. Elytra truncate behind, leaving the pygidium exposed; ventral seg- 

 ments 1 and 5 longer than the others; front cox;e small, rounded; 

 length less than .". mm. Family XXIX. MONOTOMIH.E. p. 0(>G. 



Family VI. HYDROPHTLID^E. 

 THE WATER SCAVENGER BEETLES. 



This family comprises, for the most part, oval or elliptical black- 

 ish beetles, differing from the Dytiscida? in being more convex, in 

 having the antenn-v Aiming in a distinct club instead of being fili- 

 form, and in possessing palpi which are usually longer than the an- 

 tenna? and are projected forward while swimming, while the an- 

 tennae are usually concealed beneath the head. By the inexperi- 

 enced student the palpi are, therefore, often mistaken for the an- 

 tenna-. 



The name of the family is derived from the genus Hydrophilus, 

 a word of Greek origin meaning ' ' a lover of water. ' ' As the name 



