Glossary

Arachnid: A member of the class Arachnida - includes spiders, scorpions, mites, ticks, and harvestmen. All have eight legs as adults and two main body sections in spiders specifically.
Araneae: The taxonomic order containing all true spiders.
Bullseye lesion: A wound with a darker center surrounded by lighter and then darker concentric rings; sometimes seen in confirmed brown recluse envenomations within 24–48 hours of the bite.
Cephalothorax: The front body section of a spider - the head and thorax fused into one segment. Bears the eyes, mouthparts, and all eight legs.
Chelicerae: The pair of fang-bearing mouthparts at the front of a spider. Used to grip prey and deliver venom.
Cobweb: An irregular three-dimensional web. In Theridiidae (widows and house spiders) it includes vertical 'gumfoot' threads with sticky droplets that snap up off the ground when struck by prey.
Cytotoxic venom: Venom that damages tissue at the site of envenomation. Brown recluse venom is cytotoxic.
Envenomation: The injection of venom by a biting or stinging animal. Most spider bites do not result in clinically significant envenomation.
Family: A taxonomic rank above genus. Examples include Theridiidae (cobweb spiders) and Sicariidae (recluses).
Fang: The terminal segment of a chelicera that punctures prey and delivers venom.
Funnel web: A horizontal sheet web with a tubular retreat at one end. Built by Agelenidae (funnel weavers), including hobo, giant house, and grass spiders.
Gumfoot thread: A vertical silk thread anchored to the ground with a sticky droplet at the bottom. When stepped on, it snaps the prey up into the cobweb above.
Hourglass marking: A two-triangle mark on the underside of a widow spider's abdomen. Red and complete in southern black widow; orange to yellow in brown widow.
Integrated pest management (IPM): A control approach prioritizing prevention, identification, and the least-toxic effective intervention before pesticide use.
Latrodectism: The clinical syndrome resulting from a widow spider (Latrodectus) bite - cramping pain spreading from the bite site, rigid abdominal muscles, sweating, and hypertension.
LD₅₀: The dose of a substance lethal to 50% of a tested animal population, typically expressed in mg per kg body weight. Often used to compare venom potency between species.
Loxoscelism: The clinical syndrome that can follow envenomation by recluse spiders (Loxosceles), characterized by a slowly developing necrotic ulcer at the bite site.
Necrotic lesion: An area of dead tissue. Frequently and mistakenly attributed to spider bites; most necrotic skin wounds presenting clinically have other causes.
Orb web: The classic wheel-shaped web built by spiders in the family Araneidae.
Pedipalp: A pair of leg-like appendages near the mouth. In males, modified into structures used to transfer sperm.
Sicariidae: The family of six-eyed sicariid spiders, which includes the recluses (Loxosceles).
Sphingomyelinase D: An enzyme in recluse (Loxosceles) venom responsible for the cytotoxic effects of envenomation.
Spinnerets: The silk-producing organs at the rear of a spider's abdomen.
Theridiidae: The family of cobweb spiders, including the widows (Latrodectus) and common house spiders (Parasteatoda).
Trichobothria: Fine hairs on a spider's legs that detect air movement and vibration.