458 



FAMILY SCOLYTIDAE 



In spite of its minute size, the bark beetle, in the more ordinary 

 forms, is easily recognizable once the characteristics of 

 Beetle. the build of the insect 



have been grasped. 



The beetle is usually cylindrical in shape, 

 though some specimens are spherical, as 

 e.g. Sphaerotrypes (cf. fig. 20), and brown or 

 black in colour, at times yellow or grey, 

 owing to being clothed with a dense pubes- 

 cence of this colour. The most charac- 

 teristic portion of the insect, and the one 

 which easily distinguishes it from all other 

 insects, is the antenna. The head is small, 

 prolonged either into a very short rostrum 

 or not prolonged at all, and is often en- 

 tirely concealed beneath the projecting 

 .prothorax, which forms a hood over it, as 

 in the case of many Bostrychidae. The 

 mandibles are curved, or slightly toothed, 

 and stout. The antenna is short, el- 

 bowed, and inserted between the eyes, these 

 latter being often hollowed out to allow 

 of the insertion of the antenna ; or the 

 eye may be in two pieces with the antenna 

 inserted between them. The antenna 

 does not fold back into a groove as 



in the case of Curculionidae, but when the insect is at rest is held 

 back against the side of the head. The antenna consists of three chief 

 parts: (i) The portion joining the head, which forms the lower part 



of the elbow, consists of one long joint, termed 

 the "scape," and is held more or less horizontally 

 when the antenna is in motion ; (2) a portion con- 

 sisting of a number of joints which may be as many 

 as seven or may be fewer, termed the "funiculus"; 

 (3) a knob-shaped portion which varies in shape, 

 is either solid or may have transverse divisions in it, 

 and is termed the " club." The club is inserted on to 

 the top joint of the funiculus, and with it forms the 

 upper part of the elbow, which is usually more or less 

 vertical, and at right angles to the scape. Fig. 303 

 shows this antenna with a five-jointed funiculus and 

 a club of four partitions. The antenna is of con- 

 siderable importance in the family, since the classifi- 

 cation of the various divisions is based on differences in its structure. 

 The prothorax is generally very long, often forming half the total length 



FIG. 302. 



A Scolytid Beetle (Polygraphitx}. 

 North-West Himalaya. 



FIG. 303. 



Scolytid Antenna. 



ipe ; i . funiculus of 

 live joints , C, club. 



