1987] Shattuck — Pogonomyrmex occidentalis complex 165 
P. montanus has Gaster states 2 and 3 in equal proportions (Table 
1), but shows no geographic pattern. P. subdentatus possesses states 
1, 2 and 3, with state 3 the most common (Table 1); the states are 
distributed randomly throughout the range of the species. 
Dorsum of Petiole and Postpetiole 
(PetDor and PpDor) 
All character states of PetDor are represented in P. occidentalis 
(Table 1). The character PpDor is represented by states 1, 2, 3 and 4 
(Table 1). Both of these characters show random geographic distri- 
bution; all states occur in all areas of the range of P. occidentalis 
(Figs. 25 and 26). 
Cole (1968) described the dorsum of the petiolar and postpetiolar 
nodes of P. salinus as “generally covered with numerous, strong, 
wavy, closely spaced, subparallel, usually transverse rugae” (PetDor 
states 4 and 5; PpDor states 4 and 5). In P. owyheei he described 
these structures as “not covered with numerous, strong, wavy, 
closely spaced, subparallel, transverse rugae, the nodes with or 
without irregular rugae, rugulae or striae” (PetDor states 1, 2 and 3; 
PpDor states 1 and 2). In this study all states of PetDor and PpDor 
were found to occur in both P. salinus and P. owyheei (Table 1) in 
frequencies which agree loosely with Cole’s (1968) descriptions of 
these species. P. salinus possesses primarily PetDor states 4 and 5 
(85%), but substantial numbers have states 1 and 2 (10%). Similarly, 
PpDor states 4 and 5 occur in 39% of the specimens, but states 1 and 
2 occur in 24%. In P. owyheei, PetDor states 1, 2 and 3 account for 
77% of the specimens, but states 4 and 5 occur in 23%. PpDor states 
1 and 2 are represented in 80% of the specimens, while states 4 and 5 
are only found in 7%. The broad overlap in the states of these 
characters makes them of limited value in discriminating these 
forms. 
The geographic distribution of the states of these characters 
shows a pattern similar to that of the Scape states: decreasing fre- 
quencies of states 1 and 2 and increasing frequencies of states 4 and 
5 from north to south, with a broad area of overlap from central 
Oregon into northern Nevada (Figs. 27 and 28). PpDor state 1 is 
found as far south as Washington County, Utah (100%), while state 
5 occurs only as far north as Harney and Lake counties, Oregon 
