Chemical control of Loxosceles intermedia (Araneae: Sicariidae) with pyrethroids: field and laboratory evaluation.

Bites from the recluse or brown spiders (genus Loxosceles) can cause necrotic lesions and systemic effects in humans throughout the world. In the state of Paraná, Brazil, loxoscelism is considered a serious public health problem, and Loxosceles intermedia Mello-Leitão (Araneae: Sicariidae) is associated with the majority of reported accidents. In the present research we evaluated the susceptibility of L. intermedia to pyrethroid insecticides currently used for the control of spiders in both field and laboratory conditions. In laboratory tests, the most active pesticides in descending order were microencapsulated lambda-cyhalothrin (LC50 = 0.023 mg/kg), nonmicroencapsulated lambda-cyhalothrin (LC50 = 0.047 mg/kg), deltamethrin (LC50 = 0.26 mg/kg), and cypermethrin (LC50 = 1.38 mg/kg). Cockroaches, Phoetalia circumvagans (Burmeister) (n = 30), killed with microencapsulated lambdacyalothrin, were offered to the spiders. L. intermedia fed on 63.3% of the dead cockroaches during the first 6 h of experiment; none of the spiders died during the subsequent 15 d. Microencapsulated lambdacyalothrin was chosen for application in two contiguous houses. The mean volume applied was 22.8 mg (AI)/m2. Dead spiders were found during all the inspections up to 60 d after the initial application. In total, 297 dead spiders were collected; 65.7% in the attic shared by the two homes, 10.8% inside the house that had most cracks and crevices sealed and 23.6% in the control house. The use of lambda-cyhalothrin-based products for L. intermedia control is discussed.

Evaluation of the efficacy of vacuum cleaners for the integrated control of brown spider Loxosceles intermedia

Some venomous spiders of the genus Loxosceles can reach high population densities inside and around houses. In Brazil, most spider accidents are related to Loxosceles intermedia. Control of loxoscelism should utilize integrated pest management tools, such as vacuum cleaners, to eliminate egg sacs, webs and spiders. The present study tested the efficacy of one type of vacuum cleaner (for professional and domestic use) in the control of L. intermedia populations. Cockroaches (Pycnoscelus surinamensis) were used in some tests for comparison. Vacuuming using standard accessories or a paper tube resulted in the death of all female (n=60), male (n=60), young (n=60) and just-hatched (n=60) L. intermedia, and all egg sacs (n=5) were destroyed. The removal of the plastic plate present at the bottom of the vacuuming tube inside the machine allowed some spiders to survive the vacuuming process. When kept inside a vacuum bag full of dust and debris, adult females (n=10) survived for 10 days; however, significant mortality was observed among male (n=10) and young individuals (n=10). Addition of cornstarch to the vacuum bag did not affect the spiders (n=20). Vacuum cleaners, such as the one used in the present investigation, are promising tools for integrated management of L. intermedia and other spiders in domestic environments.(AU)

Tropical house gecko (Hemidactylus mabouia) predation on brown spiders (Loxosceles intermedia)

Brown spiders (Loxosceles spp.) are venomous arachnides, successfully adapted to urban habitats in Brazil. Loxoscelism became a serious public health problem in Paraná State, especially at the capital Curitiba, where the most abundant species is Loxosceles intermedia. Hemidactylus mabouia (Gekkonidae) lizards are synanthropic predators of arthropods. In this paper, we describe the predatory behavior of the Tropical House Gecko H. mabouia on L.intermedia under laboratory conditions. Twelve geckos were observed, and all of them fed on brown spiders (n=123 observations). The attack consisted of a fast run followed by one bite on the spider's abdomen or legs. The geckos did not attack L. intermedia anterior body parts, probably due to the fangs present in this region. Two Hemidactylus individuals were killed by L. intermedia bites: during a predatory encounter, and by an induced bit on a restrained lizard. The observations summarized in this paper show that H. mabouia could be used in the biological control of Loxosceles populations in human dwellings. However, additional field studies are necessary to quantify the impact of H. mabouia predation on urban populations of L. intermedia and other species of the same genus.

A holding device for live spiders

This paper describes a new restraining device for live spiders. This device is recommended for reducing or eliminating contact between the handler and potentially dangerous spiders, as well as to avoid serious injury to the specimens.