Synanthropic habitats of the Mediterranean recluse spider Loxosceles rufescens (Araneae: Sicariidae) in central Italy

Abstract

The Mediterranean recluse spider Loxosceles rufescens (Dufour, 1820) is a public health concern due to its ability to inject venom that can cause skin lesions, referred to as loxoscelism. The spreading alarmism about recluse spiders which recently arose in Italy made it advisable to deepen knowledge about L. rufescens habitat preferences in human housing. Here, we report 14 confirmed cases of its occurrence in synanthropic habitats, and describe the housing characteristics. Our results pinpoint that traditional Italian houses of central Italy, in medieval towns and countryside, can be suitable for recluse spider colonization. The main features include the presence of walls of stone (with cracks and crevices), cellars, false ceilings, crawl spaces, wood materials (woodshed or wooden beams), and the occurrence of prey. Further characteristics which make conditions even more suitable are: large size, complex structure, and unoccupied premises. Due to its cryptic habits, even where L. rufescens is abundant, only the deployment of traps, following the recovery of a single or few individuals, revealed severe infestations. Our results confirm an unjustified negative notoriety of recluse spiders, considering that none of the inhabitants concerned, even if living in heavily infested housing, suffered from confirmed loxoscelism.