Activity patterns of a synanthropic population of the brown recluse spider, Loxosceles reclusa (Araneae: Sicariidae), with observations on feeding and mating

I recorded diel and seasonal activity patterns and behavior of the brown recluse spider, Loxosceles reclusa Gertsch & Mulaik 1940 in a free-ranging synanthropic population in northwestern Illinois. Recluse spiders are sit-and-wait predators that spend 85-90% of their nocturnal activity sitting motionless on a small network of silk they use for prey detection. Time not spent waiting for prey is typically occupied maintaining the web by laying down new strands of silk. Feeding and sexual behavior constitute a minute, but critical, portion of daily activity. Recluses were more active at night, but some were active during the day, especially in darker areas of the garage. Activity was relatively constant during the nocturnal hours. Recluse spiders became active in early to mid-May and ceased in mid-October. Beyond this, there was no consistent pattern observed in activity through these months. Sexual encounters were typically brief and similar to behavior reported in prior lab studies. Agonism was rare, but intraspecific predation was the most significant contributor to observed mortality. The most commonly captured prey in this population were spiders (Araneae, 25%), beetles (Coleoptera, 21%) wood lice (Isopoda, 15%), and crickets (Orthoptera, 13%). Recluse spiders were never observed actively searching for prey, live or dead. More than 80% of dead prey that were offered experimentally were not scavenged. Brown recluse spiders are not active scavengers; they are sit-and-wait predators that will take advantage of dead prey they happen to encounter during other activities.