90 FOREST ENTOMOLOGY. 



The general structure of the beetles themselves is somewhat peculiar. 

 The most salient feature, which gives the Scolytidse their particular 

 form, is the shape of the thorax, which is nearly always of equal 

 breadth with the elytra ; and in several genera the thorax also acts as 

 a sort of hood which covers the head, and thus, looking at the creature, 

 the head itself is very often invisible. Hence, when looking at the 

 beetle, it may be noted that the visible portions namely, thorax and 

 abdomen present together a sort of oval or cylindrical form. In 

 many species the elytra have anal hooks, which are occasionally of 

 importance in determining species. 



The under side of the abdomen is sometimes of considerable import- 

 ance, as one or more of the segments may have 

 ( - s special projections, as, for example, in Scolytus 



\ ^0J\ r multistriafus. 



\^^^\ As regards special structural details, the mandibles 



\TJ are stout, curved, or slightly toothed. The antennae. 



XJ< are short, inserted between the eyes, and form good 



c3" "F points for the discrimination of species. They are 



C? divided into three parts fig. 83 : the club (c), 



X-J the funiculus (f), and the scape (s). In German 



J w- 5 literature these parts are known by the names of 



y^ club, whip, and shaft respectively. The eyes are 



Fig. 83. Antenna of of special interest, inasmuch as they may be of 



Hylesinus crenatus. tit, r 



(Camera - lucida one body deeply cleft m the middle, or other- 

 wise distinctly divided into two parts. The legs 

 should be carefully noted, as in many species they are too small for 

 examination by a good lens, and form interesting objects when pre- 

 pared as microscopic slides. They are, as a rule, short and stout in 

 all the respective parts, with toothed femur and a five-jointed variable 

 tarsus, which is terminated by a double claw. 



The larvae are fleshy white or yellowish white, with pale yellowish 

 head. They are footless, and broadest at the head, tapering towards 

 the anal segment. The respective species cannot always be recognised 

 by their structure, but many species may be distinguished by their 

 habits and the nature of their galleries. The pupee are, as a rule, pale 

 white, and show all parts of the perfect insect. 



To the physiological biologist this group may, on the principles of 

 Natural Selection, be considered as of special interest as presenting 



