[AlexW]

“99 times out of 100, it isn’t a brown recluse north of its normal range.”
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Bugs and spiders migrate/hitchhike by being in boxes that are shipped or moved across the country.
Since the recluse is famous for being indoors, hiding in boxes and out of site, that is why they are spreading so rapidly.
They were originally found only in the southwest US.
I would not be surprised to see one anywhere.

[RC one]

I don't disagree. I still contend that 99 out of 100 alleged Loxosceles reclusa bites north of their traditional range are not, in fact, brown recluse bites. I have seen plenty of recluse bites in Texas with the infamous tissue necrosis. I have seen two possible bites in Ohio and in one of those cases, the victim's spouse had recently returned from Georgia. Recluse toxin is highly vasoconstrictive. It pinches off capillaries around the bitten area causing tissue death which then spreads. I have seen it lead to amputations of limbs in one case. It's fairly unmistakable and nothing like cellulitis arising from a staph infection secondary to an insect bite.