FAMILY SCOLYTIDAE 



459 



of the insect. It varies in shape, having a trianj^nlar appearance in the 

 spherical forms. It may be smooth and shining, or densely pitted or rugose. 

 The elytra cover the whole of the abdomen, in some instances are \ery 

 convex, and are often sharply declivous towards their apices, the declivous 

 portions having at times a scalloped appearance owing to the presence of 

 marginal teeth varying in size. The elytral surface may be smooth and 

 shining, or striate and punctate or rugose. The upper surface is often set 

 more or less densely with coarse spiny hairs, which appear in tufts on the 

 front of head (Polygraphns trenchi, pi. xlviii, fig. i), or densely on sides of 

 elytra and in the apical declivity. The under-surface is also often densely 

 hairy, the pubescence being usually less coarse in structure. 



The legs are short, many of the species walking in a feeble manner 

 on smooth surfaces, although they are able to move rapidly in their tunnels 

 in the bark and bast. The femora are toothed, the tibiae are flattened 

 laterally, and in the majority the front tibia is spined or toothed on its 



Fig. 304.— Legs of Scolytid Jketles. 



outer edge, a point used in the classification ; these tibiae are used by the 

 beetle to shovel wood-dust out of the tunnel. The tarsi are four-jointed 

 (really five-jointed, one joint being very short), and the third tarsal joint 

 may or may not be bilobed. The tarsus ends in a double claw. 



The antenna and four-jointed tarsi easily distinguish the Scolytidae 

 from the Bostrychidae. 



The larvae are small, soft, white or yellowish-white grubs, which are 

 almost always curved in the case of bark- and bast- 

 Larva, feeding forms, or verv 

 convex above and flat 

 beneath {Sphacrotrypes, fig. 315), whereas 

 in the case of the beetles which tunnel 

 into the solid wood to oviposit the larvae 

 are usually almost straight. They are in- 

 variably legless, are crinkled and corru- 

 gated, tapering in the posterior segments, 

 broadest across the thoracic segments, Fig. 3o5.-.ScoIyti.s Larva. 



