a Genus of Lamellicom Beetles. 457 



not represented the mandibles of both sexes in magnified figures, as they are 

 so much unlike each other in both male and female.) The front of the pro- 

 thorax in this sex is also armed with two small conical tubercles. 



The insect figured by Dr. Klug under the name of A. tridens of Castelnau 

 (but which appears to me to answer to Mr. MacLeay's description of A. triden- 

 tatus) has the front of the occiput produced into a long conical elevated horn 

 extending beyond the mandibles, and the middle of the prothorax has a large 

 erect horn, hollowed in front, each of its oblique sides having a small supple- 

 mental tubercle. The head of the female of this species, which is contained 

 in Mr. Hope's collection under the name A. Laportei, has the occiput termi- 

 nated transversely, just in front of the insertion of the antennae, with three 

 elevated points, one at each anterior angle and one in the middle. 



The males of ^. ceneus and A. cyanescens, figured by Dr. Klug, have the 

 head similarly produced into a long conical elevated horn, the front of the 

 prothorax very concave, the sides of the concavity beyond the middle raised 

 into two broad truncated elevated plates, each of which in the latter species 

 is armed in front with an erect horn ; but the outline figures which Dr. Klug 

 has given as representing the head and prothorax of the female of this spe- 

 cies, exhibit the occiput angularly produced and extended as far as the front 

 of the labrum (just as in the male of A. bifurcatus), whilst the prothorax is 

 represented as exhibiting the characters of the other sex partially developed. 

 If Dr. Klug be correct in giving this as a female insect, we find that the form 

 of the head offers no certain indication of sex. I should however be rather 

 inclined to suspect that this supposed female is a male with the external 

 characters of sex but partially developed, a circumstance of very common 

 occurrence in the cornuted Lamellicorns. 



With such considerations, I have but little hesitation in giving the insects 

 subsequently described under the names of A.gigas, A.armatus, and A.tuber- 

 culatus as males, although the last-named insect has been considered to be a 

 female, and A. subarmatus, A. Bilbergii and A. rotundus as females, although 

 the two former have the prothorax as strongly marked as some male insects. 

 If there be this difficulty among the larger insects, it is much greater with 

 the individuals of the small species, since some of these, which from the arma- 

 ture of the prothorax must be males, have the occiput terminated trans- 



3 o2 



