1969] 
Hlavac — Scarites 
13 
the epimeron. An internal elytral carina extends from just behind 
the level of the epimeron to the elytral apex and is enlarged pos- 
teriorly forming the internal plica. The carina rests against the 
edge of the infolded abdominal sternites. 
Antilliscaris differs from all other subgenera of Scarites examined, 
including many flightless species, in that the dorsal part of the metepi- 
meron is in the same plane as the episternum and the dorsal groove 
extends along the epimeron, i. e. the elytra-epimeron interlocking 
mechanism is absent becoming part of the elytra-episternum device 
(Fig. 18). 
Fig. 16 — Elytra-metathorax interlocking mechanism S. ( s . s.) substriatus 
Fig. 17 — Elytra-metathorax interlocking mechanism, S. (Antilliscaris) 
(EC, internal carina of elytra; Epm 3 , metepimeron ; Eps 3 , metepisternum ; 
G, metapleural groove) 
In burrowing and substrate dwelling Coleoptera, the elytral in- 
terlocking mechanisms maintain the structural integrity of the elytra- 
body joint against the forces generated in moving through a dense 
material. Lack of an integral portion of this mechanism in A ntil- 
liscaris can be explained in two, non-mutually exclusive manners. If 
the ancestral stock were not a highly adapted burrower (see below), 
then loss of epimeroa-elytra joint could be due to neutral selection 
pressure for structural integrity. Or, secondly, after becoming flight- 
less, the primary interlocking mechanism becomes the fusion of the 
elytra to each other and to the mesothorax; loss of epimeron-elytra 
joint represents post-adaptational adjustment; there is no need to 
assume a change in selection pressure for structural integrity. 
body form: S. (A.) megacephalus and 5. (s. s.) substriatus rep- 
resent extremes in body proportions with mutchleri and danforthi 
intermediate. The outline of megacephalus can be derived from that 
of substriatus by shortening the pterothorax and abdomen (Elytra 
L/W from 1.8 to 1.4 in S. and A. respectively) and the pro thorax 
