The Habronattus americanus Species Group
The H. americanus group includes three species in the region, one of which reaches its southern limit in the San Jacinto mountains of southern CA. The species group is closely related to the H. tarsalis group (Griswold places both groups into a single "americanus" group), sharing special characteristics of the male palpus and long hairs beneath the principal eyes. All three species prefer medium- to high-elevation woodland or sage habitats, and can be found on small rocks, sticks, etc. in such habitats. Microhabitat differences across species are difficult to discern, and hybridization between the pairs H. americanus / H. sansoni and H. americanus / H. bulbipes is evident at several localities within CA.
H.americanus - near Subway
Cave, Lassen Co., CA
H.americanus - Mt. Pinos, Kern Co., CA. **Note lack of hairs bundles on chelicerae.
H.americanus - Lake Almanor,
Plumas Co., CA
H.americanus - Tioga Pass, Mono Co., CA. **Note well-developed crest.
H.americanus - Myers,
El Dorado Co., CA. *Note red chelicerae.
H. americanus - H. americanus is a widespread species in the western U.S., making its way into the mountains of California as far south as San Bernardino county. Within the state H. americanus shows considerable geographic variation in several characters, including the development of the dorsal crest, color and bundling of cheliceral scales, color and patterning of femur I, and nature of clypeal iridescence. H. americanus is involved in hybridization with both H. bulbipes and H. sansoni.
H.bulbipes - Long Canyon,
Trinity Co., CA
H.bulbipes - Mt. Ashland, OR
H.bulbipes - This curious species is endemic to the Klamath-Trinity mountains of northern California and southern Oregon. Prior to the mid-90's, H. bulbipes was known only from a single individual from vic. Carrville, Trinity county. According to Griswold, the holotype specimen has a "leg I with tibia to telotarsus pale...and slightly swollen". MCH has made several collections in the vicinity of the type locality, but has yet to find populations with such a pale telotarsus. However, nearby populations do have a swollen telotarsus and "white" palps, consistent with the species description.
H.sansoni - King Creek, Lassen Co., CA
H.sansoni - near West Boulder Lake,
Siskiyou Co., CA
H.sansoni - This "species" is very confusing (or confused!). Griswold remarks that "the species is highly variable, especially in California, where each population is distinct and might be considered a separate species"! The CA forms pictured above were once considered to be a separate species (called H. kubai), but were subsequently sank back into H.sansoni. Much more work is needed to assess character variation in this "species", particularly as it relates to hybridization and potential character introgression with H. americanus.