467 
1974 ] Coyle — Genus A liaty pus 
all other populations have at most only a few very small or moder- 
ately stout setae here. 
The similar geographic variation patterns for both sexes of A. 
thompsoni indicate two areas of reduced gene flow; one between the 
northeastern populations (Tehachapi Mountain and Kernville) and 
the rest of the species, and the other between the southeastern popu- 
lations (Sierra Madre, Eaton Canyon, and Henninger Flats) and 
the rest of the species. In the former area it is likely that there is a 
paucity of suitable habitats. It is not as apparent why there might 
be reduced gene flow in the latter area. One female that was col- 
lected with the Tehachapi Mountain population looks suspiciously 
like a product of interbreeding between A. thompsoni and A. torridus 
or A. plutonis. If hybridization has occurred in this area, it could 
be responsible for some of the variant nature of the Tehachapi and 
Kernville populations. 
A possible central Sierran population of A. tho?npsoni. Seven 
A liaty pus females with only a faint depression for a thoracic groove 
were collected at Mariposa, California (0.5 mi. north of town limits 
on Hwy. 49). These are similar to A. thompsoni in all characters 
execpt posterior sigilla size and separation and PTSR. The posterior 
sigilla of the Mariposa sample are markedly smaller (Fig. 33) and 
farther apart than in A. thompsoni. The PTSR of the Mariposa 
sample ranges from four to six with a mean of 4.3, while that of 
A. thompsoni ranges from five to eight with a mean of 6.2. Except 
for CL/PC L (Fig. 31) and the condition of the thoracic groove, 
this sample is even more similar to the sympatric species, A. janus. 
It is less similar to sympatric A. calif ornicus and very unlike sym- 
patric A. ere bus. 
There are a number of possible explanations for this situation. 
Perhaps this Mariposa sample is conspecific with A. thompsoni. Per- 
haps it is a reproductively isolated northern derivative of A. thomp- 
soni. Perhaps it is a variant population of A. janus which has 
undergone a drastic shift in pars cephalica and thoracic groove struc- 
ture. Perhaps it is a product of hybridization between A. thompsoni 
and A. janus. Intensive field work in the Mariposa area is required 
to solve this problem. 
Distribution. Foothills of the Los Angeles area north into the 
Santa Ynez Mountains in the west and the southern end of the 
Sierra Nevada Mountains in the east (Map 4). 
Records. California. Kern Co.: Piute Mtns. S of Kernville, $. 
— along Water Canyon Rd., 4500-5500 ft., Tehachapi Mtns. S of 
