Abundance and distribution of Farallonphilus cavernicolus on the Southeast Farallon Island

The Farallon Islands are a National Wildlife Refuge managed by Point Blue Conservation Science

in cooperation with the Fish and Wildlife and located 27 miles from San Francisco. The Farallon

camel cricket, Farallonphilus cavernicolus (Rentz) appears to be the only endemic species on the

island, and no biological information is known regarding this species. Our objective is to determine

its abundance and distribution on the islands.We focused on quantifying the observed population of

(Farallonphilus cavernicolus) located in the caves of the South East Farallon Island by using total

counts and pitfall trapping. Our total counts show that the cave populations are fairly static, not varying

greatly from season to season. However, Rabbit Cave is an exception to this, showing significant

seasonal variation in total cricket counts with a peak near October. This may be related to the different

cave environments, Rabbit being a generally drier cave that the others. Correlation between total

cricket counts and size of caves was also assessed but none was found. Our pitfall results show that

there is a significant difference in population age structure of crickets that are found on the ground, and

those that are found on the walls or ceiling of the caves. The walls and ceiling population consisting

mostly of adults and older crickets (juveniles), and the ground population consisting mostly of younger

crickets (nymphs).