HYDROPHILlDiE. 
283 
Endomychidce. —Tarsi four-jointed, third very small. Antenna 
clubbed. 
Lathridiidce^T&rsi three-jointed. Five visible ventral segments 
(c.f. Staphylinids). 
Dermestidce. —Tarsi five-jointed. Antennae short, clubbed, and 
hidden in a groove in pro thorax. 
Byrrhidce. —Tarsi five-jointed ; small, hard compact beetles, the 
femora fitting into the coxae. 
Heteroceridce. —Tarsi four-jointed. Antennae with seven apical joints 
broadened. Aquatic, in mud. 
Parnidce. —Tarsi five-jointed, fifth long. Aquatic. 
Bostrichidce— Usually cylindrical, hard, and rugose. Tarsi five- 
jointed, basal joint small. Antennae often serrate. 
Ptinidce. —Usually cylindrical, hard, and rugose. Tarsi five-jointed, 
basal joint not small. Antennae often serrate. 
Malacodermidce. —Soft beetles, with 6, 7 or 8 ventral segments, 
antennae pectinate or serrate. 
Elateridce. —Antennae pectinate or serrate usually. Prosternal process. 
Hind angles of prothorax prolonged backwards, prothorax movable. 
Buprestidce. —Antennae serrate. Prosternal process, prothorax fixed. 
Tarsi five-jointed, basal four with pads. 
Hydkophilid^e. 
The antennae with a long basal joint , the remainder forming a club, the 
apical joints broadened , fitting below the head. Tarsi 
five-jointed , basal joint often small. 
This family is recognisable by the antennae, which are of the form 
figured (fig. 137), the broader apical joints being pubescent. They con¬ 
sist of a basal joint, a club of three to five 
joints and one to three small intermediate 
joints. They often bear a general resem¬ 
blance to Dytiscidoe , the aquatic forms having 
a similar oval form but being less compact. 
The terrestrial forms are more globose and 
rounded, but with the general facies of the 
family. They are black or dull-coloured 
insects, generally less than half an inch 
long. The head, prothorax and elytra fit 
closely, and are usually smooth and shin¬ 
ing. In the aquatic species, the hmd 
Fig. 159.— Hydrophiltjs 
OLIVACEUS. 
