EXTERNAL ANATOMY OF INSECTS. 599 
of an isosceles triangle, with the exterior side curvilinear : 
truncated elytra are generally quadrangular, sometimes 
presenting a trapezium, at others nearly a parallelo- 
gram, and at others a square. With regard to their 
proportions they vary considerably, but the most general 
law seems to be that the length shall exceed ¢wice the 
width; in some, as Buprestis Gigas, it is more than 
thrice ; in many Staphylinide they are as wide as they 
are long and sometimes wider; they are generally nar- 
rower at the apex than at the base, but in some species 
of Lycus, as L. fasciatus, &c., the reverse takes place ; in 
Telephorus they are nearly of the same width every 
where: with regard to their surface they are sometimes 
very convex, as in Moluris; at others very flat, as in 
Eurychora, Akis, &c. 
6. Appendages. These, though not so remarkable as 
those of the head and prothorax of beetles, ought not 
to be overlooked. In many Capricorns, as Acanthocinus 
Tribulus, speculifer, &c., the disk and sides are armed 
with short sharp spines; in others (Stenocorus, &c.) the 
sutural and anal angles or one of them terminate in a 
spine or tooth; sometimes the whole surface, as in His- 
pa atra, &c., is covered, like a porcupine, with a host of 
slender spines, or its sides defended by spinose lobes, as 
in H. erinacea: the humeral prominence is armed with. 
a spine pointing to the head in Acrocinus longimanus, 
and forming a right angle with the elytrum in some 
weevils, as Ethynchites spinifex ; but the most remarkable 
appendage of this kind is exhibited by Cass¢da bidens and 
its affinities,—from the centre of the sutures of the ely- 
trum rise perpendicularly a pair of long, slender, sharp 
processes internally concave, which both apply exactly 
