Graduation Date

Spring 2017

Document Type



Master of Science degree with a major in Biology

Committee Chair Name

Michael Mesler

Committee Chair Affiliation

HSU Faculty or Staff

Second Committee Member Name

Mihai Tomescu

Second Committee Member Affiliation

HSU Faculty or Staff

Third Committee Member Name

Erik Jules

Third Committee Member Affiliation

HSU Faculty or Staff

Fourth Committee Member Name

Robbin Thorp

Fourth Committee Member Affiliation

Community Member or Outside Professional

Subject Categories



Recent concerns about the ecological well-being of bee communities in California and elsewhere have increased the need for monitoring programs and studies that evaluate the impact of habitat loss and alteration on bee diversity and abundance. Such studies depend critically on the expertise of people trained in taxonomy, but their numbers have declined in recent years. My primary goal was to gain a comprehensive first-hand experience with bee identification by documenting the fauna of a previously unstudied area in the mountains of northwestern California and by writing an identification key, intended for dedicated non-specialists, to the area’s 35 species of the genus Andrena. I used a combination of aerial netting (103 hours) and pan-trapping (138 hours) to sample the bee communities at 29 sites along a 15.4 km road transect in the Horse and Grouse Mountain region of Humboldt County, California, at elevations ranging from 1200-1600 m, during the summer of 2013. The total area of my survey plots was 17.6 hectares. My collection of 3643 specimens revealed a fauna of 229 species, 20% of which were unidentified morphospecies, distributed across 39 genera and five of the six North American bee families. About half of the identified species were new records for Humboldt County based on previous taxonomic treatments. The fauna was dominated by Andrena, Lasioglossum, and Osmia, which together accounted for about half of the specimens and 15%, 14%, and 18% of the species, respectively. About half of the specimens were collected on flowers; the most important floral host was Asteraceae. With 229 species, the Horse and Grouse Mountain region supports about 12% of the bee species known for California and 6% of the species in the United States. This estimate may be too high given the large number of morphospecies (mostly Lasioglossum), but it suggests that the area may be worthy of special conservation concern. My annotated checklist sets a baseline for future surveys of the fauna and should be useful to ecologists and land managers. Also, my user-friendly key to Andrena, as yet untested on comparative novices, should make it easier to identify some of the most abundant flower visitors in the area.

Citation Style



Thesis/Project Location