The brown widow spider Latrodectus geometricus was discovered in southern California in 2003, and anecdotal evidence suggested that native western black widow Latrodectus hesperus populations are declining due to L. geometricus, but there were no quantitative studies that tested potential mechanisms. I related species abundances to temperature, humidity, human population size, human home number and elevation. I also conducted laboratory experiments on competition for dwellings, prey consumption and capture web properties. Brown and black widow abundances were highest in coastal and desert parks, respectively. Unlike L. hesperus, L. geometricus abundances did not decrease from summer toarinter. Brown widow egg sacs were more abundant than black widows at coastal parks. Brown widow abundance and human population size were positively related. Black widow abundances were negatively correlated with humidity. Prey consumption and web structure did not differ between species, but brown widows were highly successful at displacing black widows from dwelling spaces under warm conditions.
|Advisor:||Underwood, Dessie L. A.|
|Commitee:||Vincent, Leonard, Whitcraft, Christine|
|School:||California State University, Long Beach|
|School Location:||United States -- California|
|Source:||MAI 52/01M(E), Masters Abstracts International|
|Keywords:||Black widow spider, Brown widow spider, Latrodectus geometricus, Latrodectus hesperus|
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