1976] 
Peck — Beetle Genus Echinocoleus 
53 
Distribution and biology. The genus contains three species, two 
described below as new. The species are known to occur only in the 
Sonoran and Chihuahuan desert and adjacent arid regions of the 
southwestern United States in Arizona, New Mexico, and Texas 
(and probably in adjacent Mexico). All detailed collection data 
suggest that the species live in nests of Pogonomyrmex “harvester” 
and Novomessor ants. The limuloid or turtle-like body form indi- 
cates that the beetle has some need for a defensive design against 
the host ants. We may guess that the beetle is a synoekete, being 
generally ignored or indifferently tolerated by the ants. We may 
also guess that the beetles scavenge waste materials in the nests, 
because catopine beetles are generally scavengers. Dr. Foster has 
observed the beetle larvae most often in the presence of ant brood, 
and notes that both larvae and adults seem to be free living, with no 
phoretic association with the ants. 
Observations and label data suggest that adult beetles occur more 
frequently and are easiest to collect in the cooler months when the 
ants are less active. My experiences with many painful stings re- 
ceived in opening Pogonomyrmex nests in the summer in Texas and 
Mexico convinced me that this is the wrong time of year. Additional 
records of species distribution and observations of behavioral asso- 
ciation with the ants are needed. 
Larvae of two species of beetles have been recovered from har- 
vester ant nests. They are modified from the usual elongate shape 
of catopine larvae into very broad, flat forms with abundant, large, 
and thick setae. These larvae have been deposited in the MCZ. 
The record of Echinocoleus from a Pogonomyrmex nest at Selma, 
Alabama (Peck, 1973) was in error. The specimen is a Ptomaphagus 
of a species unknown to me. This alone reinforces the need for ad- 
ditional study of the catopine beetles in the nests of harvester ants. 
Echinocoleus setiger Horn 
Echinocoleus setiger Horn, 1885: 136. Lectotype here designated as male in MCZ 
(Horn colln.) bearing red label printed “Lectotype” and with the handwritten num- 
ber “2995,” and a small white label “Ari”. Type series consists of one other speci- 
men, a female, bearing a blue-green label “Paratype, 2995,” MCZ (Horn colln.). 
Both seen. Type locality: “Arizona.” 
Diagnosis. The species is distinguished by its larger size, more 
transverse pronotum with fine distinct striae and semi-erect coarse 
hairs, fine elytral striae, and spermathecal shape. It occurs in grass- 
