20 M'rAXID.TS AND rASSALID^. 



had .short straiuht liojiis without any roseniblaiice to those 

 of the type s})ecinioii. Altliough twenty-five years have 

 passed, I believe no other specimen like tliis original example 

 has been seen. It is easy to form in imagmation a scries of 

 transitional 'forms linking the short-horned Avith the fan- 

 tastically-horned phase, but there is no evidence of the actual 

 existence of such intermediates. In a paper published in 

 Trans. Ent. 8oc., 102.S, J mentioned a South American Dynastid 

 Ijcetle, Enema pan, the male of which has two different phases, 

 forjiierly regarded as specifically distinct. In the ordmary 

 form, ibund in all stages of develojunent, tlu^ head bears a 

 slender pointed horn, directed backward, and the thorax a 

 strongly forked horn directed forward. In the second male 

 phase, the thoracic horn is undivided and slender, while that 

 on the head is divided at the tip. This [jhasc, A^hich occurs 

 together with the other, is never found in different stages, 

 but is confined to specimens of full size. Smaller males 

 always belong to the normal ])hase and females are all of one 

 form. This remarkable type of dimori)hism in the male, 

 which seems to be rare elsewhere, is especially i)revalent in 

 the LucANiD^, the mandibles of which exhibit in certain cases 

 th(^ same phenomenon as the horns of Enema pan. 



If males of any abundant Stag-beetle are arranged in the 

 order of their size, the mandibles will be found to show a 

 corresponding but more rajiid increase of size, accompanied 

 by a regular advance from a simple to a less simple pattern. 

 In small specimens the inner edges are often capable of meeting 

 from base to tij), })ut in larger ones they become gradually 

 more separated and in the largest meet only at the tijis. The 

 term Priodcmt was applied by Leuthner to the first stage in 

 this development and the last stage he called Telodont. It 

 is a M'ell recognized i)rinciple that the degree of develo]mient 

 of the Lucanid mandibles, like that of the liorns of othei- 

 beetles, bears a fixed, although not a simple, mathematical 

 relationship to the size of the specimen bearing them, their 

 increase being much greater than that of the body. The 

 occu rence in certain cases of an isolated mak' ])hase, more 

 liighL' (levelo])ed than and unconnected by intermediates 

 with the ordinary form, ap])ears to form an interesting excep- 

 tion to the general rule. 



The Indian Dorcus .sntnralis (Plate II, fig. 4) is a good ex- 

 ample of this curious phenomenon. Ranging the males of this 

 species according to size, \\v find that tlieii- mandibles show 

 a gradual advance from the short anfl broad Priodont condition 

 of the smallest sj)ecimens, fig. 4 a, to a slender form, in which 

 they meet only at the tips, in tliose of full size. fig. 4/. But, 

 together with males showing tliis regular pr. grcssion, others 

 are found in the same j)laces which, although their size is 



