Concealed at diurnal rest within a silken bivouac, stealthy synanthropic predators steal micro-spaces within
our domiciles. With an outdoor and nocturnal modus operandi, Sac spiders unlawfully enter structures (especially in cool weather when prey are low in numbers) by exploiting cracks, expansions and utilities. They hide out in cracks, crevices, ceiling-wall junctions, vents, wall voids, crawlspaces, basements, sub-flooring, furniture and appliances.
Sac spiders are in the genus Cheiracanthium. Only 6 to 9.5 mm long, these suspects avoid apprehension by dropping to a surface and seeking shelter. The cephalothorax and abdomen vary in color (monochromatic brown, gray or tan), allowing them to be environmentally incognito. Mouthparts are darker with a faint dark stripe down the abdomen. Front legs are robust. Post-copulation, females place 30 to 48 eggs (shrouded in relaxed, spun silk). Numerous egg sacs are produced in a female’s lifetime and may be attended in dimensional locations.
These nocturnal predators hunt insects by both moving swiftly and waving their forelegs, not by constructing a silken-web. Sac spider venom contains a cytotoxin (a substance with a toxic effect on certain cells). It is suggested that Sac spiders cause more bites than any other type of spider.
Apprehending the Sac spider:
- Inspect corners of rooms, ceilings and behind objects.
- Sac spiders do not typically breed indoors; therefore vacuuming up sacs can be effective. (Discard the bag.)
- Remove conducive conditions like heavy vegetation adjacent to the structure.
- Exclude by sealing cracks and utilities.
- Shift Mercury vapor or “blue light” to Sodium vapor or “yellow light.”
Dr. Mitchell, D.O., Ph.D., M.P.H., B.C.E., is a Board Certified Physician & Entomologist, and serves as principal
technical specialist for PestWest Environmental. He can be reached at doc.mitchell@pestwest.com, 866-476-7378.
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