1987] Shattuck — Pogonomyrmex occidentalis complex 175 
P. subdentatus Mayr 
P. subdentatus Mayr, 1870: 971 (W). Type Loc.: California, USA. 
P. subdentatus has been considered a full species since its original 
description. The usual characters given for its identification are the 
presence of a ventral process on the petiolar peduncle (Creighton, 
1950), the arched profile of the thoracic dorsum and the cephalic 
sculpturing (Cole, 1968). The cephalic sculpturing shows only a 
small amount of variation among the species and has not been used 
in the present study. The process on the venter of the petiolar pedun- 
cle shows variation within and between species and was quantified 
as character PetVent. The arched profile of the alitrunk is unique to 
P. subdentatus. 
The presence of a process on the venter of the petiolar peduncle 
and Scape states 1 and 2 in P. subdentatus and sympatric popula- 
tions of P. salinus may cause confusion of some samples of these 
species, but the arched thoracic dorsum and reduced propodeal 
spines are characteristic of P. subdentatus. The presence of a Pet- 
Vent process and Scape states 1 and 2 in some sympatric popula- 
tions of P. salinus may indicate gene flow between these two species, 
but the lack of other characters of P. subdentatus in these popula- 
tions distinguishes the species clearly and suggests no gene flow 
between them. Further study will be necessary to resolve this 
inconsistency. 
Key to the Species of the 
Pogonomyrmex occidentalis Complex, 
Based on Workers. 
la. Mandible with 6 teeth; venter of postpetiole with a strong, tri- 
angular tooth P. anzensis 
lb. Mandible with 7 teeth; venter of postpetiole rounded, without a 
tooth-like process 2 
2a. Interrugal spaces of head smooth and shiny, without puncta- 
tion; dorsum of petiolar node without transverse rugae 
P. subnitidus 
2b. Interrugal spaces of head densely punctate and opaque, with a 
beaded appearance; dorsum of petiolar node variable, but 
often with at least 1 ruga present posteriorly 3 
