34 BULLETIN 1091, U. S. DEPARTMENT OF AGRICULTURE. { Bun^N^l, 
trapping for speetahilis on its own characteristic mounds one catches 
a large percentage of merriami. 
On two separate occasions Yorhies has observed the smaller species 
running over the mounds of the larger, actually carrying away the 
grain which had been placed to entice the larger when it might 
appear. (In these cases the larger species did not put in an appearance 
until near morning.) Furthermore, the dens of merriami are often 
connected by distinct runways with those of spectdbilis, indicating 
much traveling or visiting. That this is probably not friendly visit- 
ing is suggested by the certainty with which an individual of the 
larger species will strike and kill one of the smaller when they are 
placed together in the same inclosure. The word "thief" expresses 
this suspected relationship better than would the term " parasite. " 
It is not to be expected that such obvious shelter retreats as the 
mounds of spectahilis should fail to attract the attention of other 
animals. We have found a small gecko (Coleonyx variegatus) . 
scorpions of two or three undetermined species, and certain in- 
sects (of the Order Orthoptera) to be very common inhabitants 
of the dens. With the exception of the parasitic insects the most 
common are wingless locustids (OeuthopJiilus spp.) and the pecu- 
liar wingless females of a species of cockroach {Arenivaga erratica). 
These two are seldom absent when a burrow is excavated, the female 
cockroaches being abundant, although the Avinged males have never 
been taken in the burrows. 
Cary's observations at Monahans, Tex., and those of others at 
numerous localities, combined with our own. show that at various 
times the dens furnish protection and shelter for various species 
of cottontail rabbits (Sylvilagus) , ground squirrels {Oitellus and 
Ammospermophilus) . wood rats {Xeotoma) . grasshopper mice 
{Onychomys) . rattlesnakes (Cro talus) . and most of the common 
lizards. Of these the ground squirrels Gitellus tereticwudus and 
Ammo s p> er mop hit us Jiarrisii are most often noted on the Range Re- 
serve using the dens as a retreat, the Ammospermophilus seldom 
being observed to enter any other kind of burrow. It should be 
added that the total observations include dens which have been 
deserted by their rightful owners. 
NATURAL CHECKS. 
The enemies of the kangaroo rat are not determined in detail, or 
as to relative importance, but the badger (Taxidea taxus berlan- 
dieri) and the kit fox, or swift {Vulpes macrotis neomexiccma ) . 
may well be foremost. Dens which have been deeply excavated by 
badgers are frequently seen, and sometimes two or three badger 
tunnels penetrate one burrow system. Dens thus despoiled are 
