Classification of the Coleopterous family Dynastid/e. 353 



remarkable tendency to dimorphism seen in males of other 

 genera of the group. The size is little less than that of 

 the type specimen, but the cephalic horn is only a third 

 of the length and bifurcated at the end, and the thoracic 

 horns are represented by a pair of nodular processes occu- 

 pying the same position, but showing no indication of the 

 very peculiar form assumed in its fuller development. 



I have not seen the female. 



This insect is exceedingly like Aleidosoma siamense, 

 Lap., in all respects except the position, shape and direc- 

 tion of the thoracic horns. It is a little more elongate, the 

 margins of the prothorax are rather straighter and more 

 parallel behind and its surface more smooth and shining, 

 and the pygidium is more closely rugose. 



In making the genus Aleidosoma, Laporte declared that 

 it was not in his opinion really entitled to generic separa- 

 tion from Chalcosoma, but it is still more closely related to 

 Enpatorus and males of A. siamense in a certain stage of 

 development are almost identical in form to Ewpcttorus 

 Hardivichei, Hope, differing only in the fine sculpture of 

 the surface of the body. They agree also in the broad 

 multidentate outer lobe of the maxilla, which is very 

 different from the acuminate form of that of Chalcosoma, 

 in which the mentum is also much longer and narrower. 

 C. Beccarii, Gestro, is an intermediate having in my 

 opinion more points of affinity with Enpatorvs than with 

 Chalcosoma. The mentum is of the same form and the 

 maxillae are blunt at the end, but with a sharp tooth be- 

 neath, which is not found in the other species. The male 

 does not possess the anterior thoracic processes of Eupa- 

 torus, but the small importance of the sexual armature is 

 shown by the curiously different forms assumed in E. 

 siamcnsis and E. hirmanio's, which are so closely alike in 

 all other respects. The discovery of other forms may yet 

 bridge the interval by which Chalcosoma is divided from 

 Eupatorus, but for the present the form of the mentum and 

 maxillae, together with the great elongation of the legs in 

 the male, serves to distinguish C. Atlas, L. { = Phidias, Bl.) 

 and C. Mollenkamjn, Kolbe, while I refer to Eupatorus the 

 following species : — E. Hardioioliei, Hope (with var. Cantori, 

 Hope), gracilicornis, Arrow, siamcnsis. Lap., hirmanicus. 

 Arrow, Beccarii, Gestro, and the following Australian 

 species, which, although in many respects the most diver- 

 gent of all, has considerable similarity to E. Beccarii. 



TRANS. ENT. SOC. LOND. 1908. — PART II. (SEPT.) 23 



