1969] 
'Hlavac — Scarites 
15 
the large number of carabid species occupy three locomotory adaptive 
zones: arboreal (several tribes), ground in the broadest sense in- 
cluding soil surface and leaf litter (most tribes and species) and 
burrowing (primarily the Scaritini). All terrestrial zones available 
to a beetle are exploited by the Carabidae. Breadth of adaptation for 
the family and high local diversity (see Darlington 1943 for data) is 
the result of adaptive radiation and species packing via competition. 
The energetics of food searching differs between the zones. If the 
energy expended by a ground species in searching a unit area is taken 
a base point, then both arboreal forms, which fly and climb vertical 
surfaces, and burrowers producing a. new section of burrow expend 
more. In the absence of competition from related taxa, as in the 
mountains of Puerto Rico for a large carabid, if ecological shift 
occurs in a new colonizer it should be in the direction of increased 
efficiency of search behavior. 
The burrowing mechanism of Scaritine carabids consists of many 
interrelated morphological and behavioral adaptations. Evidence that 
several structures and proportions differ from a known burrow pro- 
ducer is presented above and can be interpreted as indicating a re- 
organization of the burrowing mechansm for a ground surface 
existence. 
The steps taken by a species after colonizing a depauperate habitat 
island are : initial adaptation, ecological shift, loss of dispersal power, 
speciation, and adaptive radiation (MacArthur and Wilson 1967, 
Chap. 7). Speciation and loss of dispersal power have occurred in 
A ntilliscaris ; there is evidence for ecological shift. That an adaptive 
radiation has occurred in A ntilliscaris is an exciting possibility and 
should stimulate further field work. 
behavior: A specimen of S. (A.) mutchleri is currently being ob- 
served. While a full report of its behavior is planned, the following 
observations are germane at this point. The beetle has not con- 
structed an elaborate burrow system under conditions where sub- 
striatus and subterraneus would (Hlavac 1967). Daylight hours are 
spent under retreats or in concealment burrows, about 2 body lengths 
long, dug in areas where the soil has not been highly compressed. 
During the night, this animal has eaten food placed on the surface 
and fallen into a small pitfall trap in the center of the container 24 
nights out of 37. These fragmentary data are consistant with the 
hypothesis of ecological shift. 
biogeography : The factors responsible for the high frequency 
of wing atrophy in montane carabids have been analyzed by Darling- 
ton (1943). He pointed out (1939, pp. 79-80) that mountains over 
