Overview of two introduced spiders, Tegenaria agrestis walckenaer and Tegenaria duellica simon (agelenidae), in Washington State Life history development, interactions and medical importance

The European spider Tegenaria agrestis was introduced into Washington State in the 1930s and is a concern today due to the suspicion that its bite causes necrotic lesions. The introduction of the closely related congener species, Tegenaria duellica, in the 1960s may influence populations of T. agrestis through ecological similarities and competitive interactions. I examined three aspects of the potential medical importance of T. agrestis. First, the bacterial diversity was surveyed to determine if the spider carries any pathogenic bacteria, second, the ability of the spiders to transfer methicillin-resistant Staphylococcus aureus (MRSA), and third, the hemolytic activity of the venom. We found ten genera of bacteria on the exterior surface of the spiders, and none of the spiders exposed to MRSA transferred this pathogen. The hobo spider venom was not deleterious to vertebrate red blood cells. Because the occurrence of intraguild predation between closely related spiders can effect population numbers, an investigations of the interactions between these species were conducted under laboratory and field conditions. Studies were, the time taken to utilize a congener web for prey capture; antagonistic interactions between adult female conspecifics and congeners; antagonistic interactions between similarly sized juvenile congeners; and field experiments to assess the survivorship of conspecific and congener: adult males and adult females and similarly sized juveniles in a simplified habitat. Both species readily accepted prey on the web of its congener. Laboratory and field trials indicated that T. duellica was the dominant surviving species throughout the season. Differences in microhabitat selection were found with overall similarities in macrohabitat. Because of overlaps in biological parameters and their propensity to share similar niches, comparative trials were conducted to investigate overlaps in habitat selection around homes in urban environments, assess the seasonal life history and record the growth and development of the congeners in the United States. A two year life cycle is described for both species. Tegenaria duellica maintained a size advantage over T. agrestis from March through August however; the majority of T. duellica were smaller than T. agrestis during the months of September and October