Loxosceles reclusa (Gertsch & Mulaik, 1940)

Brown recluse

The spider everyone fears and almost no one in Ontario has ever actually seen.

Order: Araneae
Family: Sicariidae
Group: Spiders
Ontario status: NOT established, myth-buster dossier; occasional intercepted specimens only

Why it matters

It matters because of the damage the myth does: thousands of skin lesions across North America are blamed on a spider that was never there, delaying real diagnoses, staph and MRSA infections, diabetic ulcers, vasculitis. Knowing what is NOT in Ontario is public-health work.

Origin

The south-central United States, its real range is roughly Kansas to Texas to the lower Midwest. Ontario is far outside it.

Behavior

True to its name, reclusive, nocturnal, non-aggressive. Bites only when trapped against skin in clothing or bedding.

Living conditions

In its home range: undisturbed indoor clutter, closets, attics, woodpiles. In Ontario: essentially nowhere, it cannot establish breeding populations in our climate.

Signs of presence

In Ontario: none reliably. Reports without a captured specimen are not evidence.
A spider with exactly six eyes in three pairs (needs magnification to check)
Irregular webs in undisturbed clutter (in its actual range)

Weaknesses

Cannot survive Ontario winters outdoors or establish indoors here
Every 'recluse' found in Ontario has been a misidentification or a lone hitchhiker
Non-aggressive; even in its home range, bites are uncommon
Easily distinguished by its six eyes, if it has eight eyes, it is not a recluse

Myths and facts

Myth Brown recluses infest Ontario homes.
Reality Not established in Ontario, virtually all 'recluse bites' here are misdiagnosed skin conditions or other spiders. Arachnologists use a rule of thumb: no confirmed specimen, no recluse.
Myth You can identify a recluse by the violin marking on its back.
Reality Many harmless spiders have violin-like marks, and some recluses barely show one. The reliable character is the six-eye arrangement, three pairs, which needs magnification to see.

Research notes

Morphology

Body 6-12 mm; uniform tan to brown; the definitive character is six eyes in three dyads (most spiders have eight). Long thin legs; no spines. The 'violin' marking is unreliable and should never be the sole criterion.

Diagnostics

Six eyes in three pairs, confirmed under magnification, plus range plausibility. In Ontario, range alone rules it out, demand a voucher specimen for any claim, and expect it to key to something else.

Easily confused with

Spitting spiders (Scytodes thoracica) Also six-eyed, but with a strongly domed carapace and much shorter legs; common and harmless in Ontario.
Woodlouse hunter (Dysdera crocata) Eight eyes, massive forward-projecting jaws, reddish carapace, a completely different spider often called a recluse by mistake.

Life cycle

Adult: Adults live 1-2+ years
Egg: 30-50 eggs per sac; female guards the sac
Egg to adult: Up to a year in temperate conditions
Generations per year: One in its native range
Nymph or larva: Slow development; spiderlings resemble pale adults

Development

Egg to spiderling to adult through successive molts. Remarkably long-lived for a spider: adults can survive 2+ years, and months without food or water.

Reproduction

Males wander to find females; females produce several sacs per season. Low dispersal ability, populations are highly localized, which is one reason it has not spread to Ontario.

Distribution

Global: North American endemic; congeners (including the medically significant L. laeta) in South America and the Mediterranean
Native range: South-central United States
Ontario: Not established; occasional intercepted specimens only. No breeding populations documented.

Ecology

In its native range, a synanthropic predator of small arthropods in undisturbed microhabitats. Its limited dispersal and cold intolerance define its range boundary well south of Ontario.

Resistance

Unknown, no documented resistance of note.

IPM implications

None in Ontario beyond identification and reassurance. The professional protocol for any 'recluse' report: collect the specimen, examine the eyes, document the finding, and use the moment to educate, including referring suspected bite lesions to medical care, since the real causes (bacterial infection, etc.) need treatment the spider story delays.

Chemical ecology

Venom contains sphingomyelinase D, the enzyme behind dermonecrotic loxoscelism in a minority of verified bites. The biochemistry is real; the epidemiology in Ontario is not, venom chemistry does not create spiders where none live.

Genetics and DNA

A draft whole-genome assembly for L. reclusa is published (3.26 Gb, NCBI GCA_001188405.1; listed in arachnid genomics reviews), a draft, not chromosome-level.

Taxonomy

Order Araneae, family Sicariidae. Authority (Gertsch & Mulaik, 1940). The only Loxosceles of medical note in North America; Ontario has no established sicariids.

Open questions

Why range expansion has stalled despite climate warming; true bite incidence even within the native range is overestimated by orders of magnitude.

References

Foelix, R.F. (2011). Biology of Spiders, 3rd ed., Oxford University Press.
Vetter, R.S., UC Riverside spider-bite myth research (various publications).