258 Beetles 



them when diving or swimming below the surface, by having a bubble 

 attached to the posterior tip of the body. The hindmost legs are broad 

 and paddle-shaped, and fringed with long stiff hairs. The whirligig- 

 beetles can fly, but usually have to climb up on some weed or stick pro- 

 jecting from the water in order to make a start. They can make a curious 

 squeaking noise, probably a call to other whirligigs, by rubbing the under 

 side of the wing-covers against the end of the body. When handled, most of 

 these beetles emit an ill-smelling whitish liquid. 



In the winter the whirligigs lie torpid in mud among the roots of water- 

 plants, coming out by twos and threes in the spring. The eggs are laid 

 usually on the leaves of some water-plant, and the curious slender larva 

 (Fig. 351) is provided with long tapering lateral gills fringed with fine hairs. 

 There is a pair of gills on each abdominal segment. It feeds on water- 

 insects and other small aquatic animals, and probably also on the "tender 

 parts of submerged plants." The pupae of but few species are known. 

 That of a common English species lies in a grayish silken cocoon spun on 

 some water-plant above the water's surface. 



TRIBE CLAVICORNIA. 



The clavicorn beetles, or those with clubbed antennae, show much variety 

 in the character of the terminal thickening of the antennae (Fig. 340, 4-7), 

 which is the characteristic structural feature of the members of the group, 

 and from which the tribal name is derived. The tribe includes, too, beetles 

 of widely different habits, some aquatic, others terrestrial, some predaceous, 

 others plant-feeding, others living on dry stored grains, woolens, and still 

 others feeding on carrion. They have indeed little in common and the 

 grouping is largely a matter of convenience in classifying. The more im- 

 portant families of this tribe can be separated by the following key: 



Aquatic; legs fitted for swimming (Water-scavenger beetles.) HYDROPHILID^E. 



Terrestrial; legs not fitted for swimming. 



Antennae moniliform, i.e., with segments bead-like; elytra usually covering only basal 



half of abdomen (Rove-beetles.) STAPHYLINID^E. 



Antennae moniliform or sub-monilif orm ; elytra covering most of the abdomen: brown 



or reddish species (Grain-beetles, etc.) CUCUJID.E. 



Antennae capitate, i.e., ending in a little ball, or clavate. 



Large insects, the smaller not much less than half an inch long (except Catops); 



body usually flattened (Carrion- or burying-beetles.) SILPHID^E. 



Small insects, mostly less than one-half inch long; body thick and convex above. 



(Larder-beetles, etc.) DERMESTID^;. 



In the same ponds and pools with the predaceous diving-beetles and 

 whirligigs may be found other water-beetles, black, shining, and often of 

 large size, which are readily distinguished by their short concealed clavate 



