Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Establishment of the brown widow spider (Araneae: Theridiidae) and infestation of its egg sacs by a parasitoid, Philolema latrodecti (Hymenoptera: Eurytomidae), in French Polynesia and the Cook Islands.

Abstract

This paper presents two newly established species for French Polynesia: the invasive brown widow spider, Latrodectus geometricus C. L. Koch, and its potential biocontrol agent, the parasitoid wasp, Philolema latrodecti (Fullaway). The brown widow spider was recorded from the island of Moorea in 2006 and, since that discovery, the occurrence of this species has expanded to two of the five archipelagos of French Polynesia including the main island of Tahiti and four of the Cook Islands. Although the tropical climate contributes to the establishment of L. geometricus, a biotic factor, P. latrodecti, may restrain population from demographic explosion. This eurytomid wasp is present in French Polynesia and is a parasitoid that has been used in biological control of the southern black widow Latrodectus mactans (F.) in Hawaii. This wasp could become a significant limiting factor for L. geometricus distribution on these islands, as it was found in 31% of the Tahitian brown widow spider egg sacs that were dissected. However, thus far, the wasp was only found on Tahiti in association with the brown widow spider. Although the brown widow is generally considered to be less toxic than its black widow relatives, it remains of medical concern in French Polynesia because reactions to its bites can, at times, be severe. The spider remains of public concern because it is a novel species; it has the word widow in its name and dark morphs are mistaken as black widows.