Population Dynamics of the Red Widow Spider (Araneae: Theridiidae)

Populations of the red widow spider, Latrodectus bishopi, in native Florida scrub at the Archbold Biological Station were monitored annually on ten ≈0.5 ha transects in late winter from 1987 to 2000. Of 398 L. bishopi detected in the study, all but three had their silken retreats built in palmetto leaves. L. bishopi at rest in retreats in saw palmetto (Serenoa repens) were higher above the ground (≈0.5 m) than spiders in scrub palmetto (Sabal etonia) (≈0.3 m). From a peak of 31 spiders/ha in 1989, the average L. bishopi density declined exponentially to only 0.3 spiders/ha in 1997, after which L. bishopi densities began to recover. Burning of scrubby transects in spring or summer appeared to have no affect on subsequent L. bishopi populations. There were no significant correlations between L. bishopi population density and local temperature or precipitation data. These results suggest that undescribed biotic factors may regulate populations of the red widow spider in a density-dependent fashion.