712 EXTERNAL ANATOMY OF INSECTS. 



as A. lineare, &c. a ; in others it is extremely short and 

 thick, as in Copris, &c; a mere appendage in Evania ; 

 it is shorter than the elytra in Trox ; of the same length 

 in most beetles ; longer in Melolontha, Hister, &c; dis- 

 proportionately so in Staphylinus: though usually of the 

 same width with the trunk, in many Mantidce it is much 

 wider b ; and more slender in the Libellulina, Myrme- 

 leon, &c. 



vi. Arms and Appendages . These are various ; and 

 may be considered under the following heads : processes; 

 organs of respiration, motion and prehension-, ^weapons; 

 and other anal appendages the use of which is unknown. 



1. Processes. Under this term I include all promi- 

 nences of whatever kind, whether tubercles, teeth, spines, 

 or horns, that arm any part of the abdomen. Many of 

 these are sexual characters, and have been sufficiently 

 described in a former letter d ; I need not therefore detain 

 you long on this head. Of the first kind is a remarkable 

 elevation that distinguishes the second ventral segment 

 ofScolytus Destructor (Ips Scolytus Marsh.) or of a species 

 allied to it e ; in S. pygmceus (I. multistriatus Marsh.) the 

 same segment is armed by a flat horizontal tooth or horn; 

 in an Aradus from Brazil, before alluded to f (A. lami 

 natus K. MS.), the margin of the abdomen is surrounded 

 by eight flat subquadrangular laminae; in another species 

 figured by Stolls, it is cut out into bays by a number of 



a Roemer. Genera, &c. t. xxiv./. 4. b Stoll Spectr. t. vii. 



c Plate XV. Fig. 10-23. d See above, p. 339— . 



e This tubercle I find only in a specimen from Sweden, sent to me 

 by Major Gyllenhal, but not in any British one I possess. In this spe- 

 cimen the declivity before mentioned (see above, p. 709.) is observa- 

 ble in theirs* segment, but in the others it is formed by the second. 



f See above, p. 617. B Punaises, t. xiii. /. 84. 



