EXTERNAL ANATOMY OF INSECTS. 711 
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- 
proportionably so in Staphylinus : though usually of the 
same width with the trunk, in many Mantide it is much 
wider* ; and more slender in the Lzbellulina, 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®; I need not therefore de- 
tain you long on this head. Of the first kind is a re- 
markable elevation that distinguishes the second ventral 
segment of Scolytus Destructor or of a species allied to 
it¢; in S. pygmaeus the same segment is armed by a 
flat horizontal ¢ooth or horn; in an Aradus from Bra- 
zil, before alluded to* (A. laminatus K. MS.), the mar- 
gin of the abdomen is surrounded by eight flat sub- 
quadrangular lamine; in another species figured by 
Stoll‘, it is cut out into bays by a number of denticu- 
lated teeth; and in Coreus paradoxus by long spinose 
* Stoll Spectr. t, vii. > Prate XV. Fic. 10—23. 
© See above, p. 338—. 
4 This tubercle I find only in a specimen from Sweden, sent to 
me by Major Gyllenhal, but not in any British one [ possess. In 
this specimen the declivity before mentioned (see above, p. 708.) is 
observable in the first segment, but in the others it is formed by the 
second. 
® See above, p. 615. * Punaises, t. xii. f. 84. 
