H 
Psyche 
[March 
(L/W from 0.7 to 0.5) and by increasing the size of the head until 
it is 1.36 the length of the prothorax (0.82 in substriatus) and until 
the length of head and mandibles is 1.1 the length of the elytra (0.6 
in substriatus ) . 
A partial explanation of the shortening of the elytra is the atrophy 
of the flight mechanism. Differences in size between the head and 
prothorax can be looked at in terms of differences in muscle volume, 
i. e., a relative decrease in volume in the prothorax and a relative 
increase in the head. The prothorax houses most of the muscle vol- 
ume responsible for its movement as well as that which moves the 
head and proleg (Larsen, 1966, p. 140), while the head encloses 
muscles responsible for the movement of its appendages. Ventro- 
dorsal rotation of the head and prothorax are principal actions in 
burrowing, decrease in muscle volume for performing these actions 
indicates a shift in or absence of burrowing behavior. The large head 
implies a large mandibular adductor muscle and this along with the 
large carnassal areas of the mandibles could be an adaptation for 
seizing and breaking open large prey objects. 
ecological shift: Of the eight known montane species of cara- 
bids on Puerto Rico listed below, three are Scarites, and, with Oxy- 
drepanus coainensis Mutchler, scaritines make up 50% of the known 
carabid fauna. On Jamaica, an island of similar size (4500 sq. mi. 
vs. 3400 for P. R.) 17 montane restricted species are known, nine 
of which are Colpodes ; there are no Scarites (Darlington, 1941). 
As currently known, the montane biota of Puerto Rico is unique in 
the Greater Antilles in not having a large number of ecologically 
variable Colpodes. The size range of Puerto Rican species is 2.0 to 
35 mm with the following distribution: 
1-5 mm, 4 spp., Oxydrepanus coamensis Mutchler, 2 mm; 
Bembidion portoricense Darlington, 3.5 mm; 
Perigona microps Darlington, 2.9 mm ; 
Phloeoxena portoricensis Darlington, 4.5 mm. 
5-10 mm, 1 sp., Colpodes estriatus Darlington, 4.0-6. 7 mm. 
10-20 mm, 2 spp., A ntilliscaris danforthi, 14.6-16.0 mm; 
Antilliscaris mutchleri , 1 2.0-18.0. 
30+ mm, S. (A.) megacephalus , 30-35 mm. 
Antilliscaris is thus the largest carabid taxon, is at the apex of the 
size pyramid and is doubtless one of the top predators among ground 
invertebrates in this habitat. 
It is useful to look at the mountains of Puerto Rico as habitat 
islands and to analyze the large Scarites fauna in the manner of 
MacArthur and Wilson (1967). In harmonic continental biotas, 
