12 
Psyche 
[March 
45-59% and the basal molar part ranges from 17-21% of the total 
length. In Antilliscaris then, the median caranassals are twice as 
large and the molar area half the relative size of the corresponding 
areas of substriatus. 
If it can be assumed that these structural differences correlate with 
behavioral differences, then the condition in Antilliscaris may reflect 
3 types of such differences. The mandibles of substriatus and sub- 
terraneus are used to loosen material from the head wall of the bur- 
row, in mating and, of course,- in feeding. Some substrate loosened 
by the protibia is compressed further and compacted into a part 
of the stable burrow system by the vertex of the head and pronotum 
(Hlavac, 1967, and unpublished observations). The smaller molar 
area in Antilliscaris could indicate either that these animals burrow 
through a less dense, more easily compacted, substrate than Scarites 
s. s. or that they do not burrow at all. Secondly, the differences in 
mandible morphology may reflect differences in feeding behavior (see 
comments on body form, below) or mating. 
flight mechanism: Antilliscaris represents an extreme point in 
the atrophy of the flight mechanism. The fused elytra are immovably 
joined to the mesathorax at two points, the posterior part of the 
mesatergum is tucked around and closely pressed against the anterior 
contours of the elytral cavity and secondly, the elytral hinge mech- 
anism is solidly fused to the anterior part of the mesatergum. 
The volume enclosed by the metathorax is reduced ; externally, 
this is seen most clearly by comparing the relative size of the lateral 
portion of the sternum and the L/W ratio of the episternum in 
flying and wingless species. In substriatus the narrowest lateral part 
of the sternum is about half the mid-line length and the L/W of 
the episternum is about 4, whereas in inutchlei-i the lateral portion 
is 20% of the mid-line length and the L/W of the episternum is 
about 1. The central part of the sternum is also shortened in Antil- 
liscaris but less dramatically; the mid-line in substriatus is equal to 
the length of tthe first 3 1/2 abdominal sternites while in mutchleri 
it is equal to the length of the first 22/3 abdominal segments. The 
vestigial wings of ?nutchleri are very small (.375 X .100 mm) and 
circular in cross section in a specimen examined in fluid. 
In the Scaritini there are usually 3 lateral elytra-thorax and abdo- 
men interlocking mechanisms. (Hlavac, unpublished observations.) 
The anterior lateral edges of the elytra fit into grooves on the dorsal 
rim of the mesepisternum, mesepimeron and metepisternum (Fig. 17). 
The dorsal part of the metepimeron slopes inwards; the elytra curve 
slightly outwards at this point and rest on top of the flat surface of 
