COLEOPTERA. 



727 



Sub-order 3. POLYMORPHA. 



Antennae usually clubbed or toothed on inner border. This a loosely 

 defined sub-order of some fifty families of very varying importance. 



Fam. 10. Paussidae. Antennae usually with two segments. Long 

 elytra but not covering end of abdomen. Tarsi with five joints. Small 

 beetles of very bizarre appearance frequenting ant's nests. They seem 

 to be popular with the ants, whose larvae and eggs they eat, but the reason 

 of their popularity is not very apparent. Paussus. 



Fam. 11. Gyrinidae. Antennae short. Meso- and meta-thoracic legs 

 adapted for swimming. Each eye divided into two. These beetles are 

 termed whirligigs from the mazy dance they perform on the sxirface of 

 the water. They are emphatically surface dwellers, and if they dive they 

 soon ascend again. The larvae are long, and the nine abdominal segments 

 bear each two feathered branchiae. Both larvae and imagos are car- 

 nivorous. Gyrinus, with eight British species, and a single species of the 

 nocturnal Orectochilus, represent the family in this country. 



Fam. 12. Hydrophilidae. Antennae with less than eleven segments, 

 sub-divided into three regions. Palps of first maxilla often longer than 

 antennae. Five visible segments in abdomen. 

 A cosmopolitan, large family mostly aquatic. 

 Hydrophilus piceus(Fig. 460), British, carries 

 a layer of air, renewed by the action of the 

 antennae, entangled in hairy patches beneath 

 the body ; among these patches the tracheae 

 open. Egg-cocoons are unusual amongst 

 Coleoptera, but many members of this family 

 construct them. Spercheus, British, carries 

 its cocoons beneath its abdomen. The larvae 

 are carnivorous and as a rule aquatic. 



Fam. 13. Platypsyllidae. Wingless. An- 

 tennae with three segments, the last of which 

 is sunk in the second ; both second and third 

 bear long setae. The mentiim is trilobed 

 posteriorly. This family consists of a single 

 species, Platypsyllus castoris, which lives and 

 lays its eggs amongst the hair of the Beaver 

 in both the old and new world. 



Fam. 14. Leptinidae. Antennae with eleven 

 joints, thickening towards tip. Eyes absent 

 or imperfect. Five tarsal segments. Elytra 



conceal abdomen. Two genera, Leptinillus which like Platypsyllus lives on 

 beavers, and Leptinus which lives on mice and in the nests of humble- 

 bees, each with a single species, constitute this family. The latter genus 

 is British (Fig. 463). 



Fam. 15. Silphidae. Straight, clubbed antennae, usually eleven- 

 segmented. Tarsi iisually five-segmented. Abdominal segments usxially 

 five or four, rarely seven, visible, but the anterior three terga at least are 

 membranous. The Carrion-beetles form a large cosmopolitan family, 

 very varying in size. The well-known burying beetles by making tunnels 

 under small dead mammals and birds, succeed in interring them, and then 

 devour them in peace. Many species dwelling in caves are sightless. 

 Others live amongst moss or under bark. The larvae are active with 



FIG. 463. Leptinus testaceus. 

 Britain. From Sharp. 



