There were many moments of discovery on my trip to sw Oregon, many moments of joy and wonder, many ‘Yeehaw!’ moments. But, possibly because it was so unexpected (although it shouldn’t have been), the moment when the most thrilled adrenaline rush of the trip coursed through my veins was when Sam McNally said, in his usual low key way, ‘I found a scorpion’. I hopped up from my examination of the underside of a log, and hustled (well, as much as this old man can ‘hop up’ or ‘hustle’) over to get a look before it disappeared, although it didn’t end up moving at all, possibly due to the relatively low temperature.
Based on the location (Applegate Ridge in Jackson County, Oregon) I was pretty sure it was Uroctonus mordax (commonly called the California forest scorpion or Oregon forest scorpion, though I prefer the term western forest scorpion, since its range is not confined to either of those two states), but scorpions are difficult to positively identify in the field, and there is always the possibility of a range extension in under surveyed groups like scorpions, so I collected it after a few photos. A few minutes later (and only a few yards away) Sam uncovered another scorpion, but since it appeared to be identical to the first one, albeit somewhat larger, I merely took several photos, grokked in the fullness of its presence, and then left it in peace after replacing the roof to its house.
30 years ago I found a couple of these scorpions in the Columbia River Gorge, and I was shocked to find scorpions in a forest, having it in my head that scorpions only lived in deserts. But my friend Craig Sondergaard knew immediately what they were, and I have unsuccessfully been hunting for more of them ever since. Like most scorpions western forest scorpions fluoresce under UV light, and I’ve heard of them being found by nighttime hikers with UV flashlights (especially on the Dog Mtn trail on the Washington side of the Columbia River Gorge), but though I’ve tried that a few times I have not succeeded in finding one.
There doesn’t seem to be a lot of information out there specific to this species. In fact arachnological taxonimists can’t even decide if it belongs in the family Vaejovidae, or Chactidae, or neither. I wrote about scorpion UV fluorescence and mating rituals in my profile of Paruroctonus boreus, and that information is also valid for Uroctonus mordax. Based on their presence in much more humid areas than Paruroctonus boreus I would guess that Uroctonus mordax is more prone to desiccation, but the limits to its northern range suggest that it is also less tolerant of prolonged cold, although some of its habitats that are over 1,000’ elevation are probably snow covered for several months a year. But these are all suppositions, and I can find no information that verifies any of them.
And I am trying to be okay with leaving them mysterious, because there is only so much that we can ever know about the life as experienced by any living creature, especially one that lives deep in the shadows and the night as western forest scorpions do. They seem such perfect little predators, and so prehistoric, with a basic body plan that’s been around for 400 million years. And yet, at least for the two species I’ve found, they are much more inclined to move away than to attack. Provided one is not allergic, neither Uroctonus mordax or Paruroctonus boreus have a medically significant sting, apparently somewhere on a par with a bee or yellowjacket sting, and the venom is so unproblematic that it’s chemical composition hasn’t even been studied. So, while it is probably not wise to let your baby crawl around in the brush in the dark where western forest scorpions are known to prowl (or even where they don’t, fer’gosh’sakes!), the rest of us can just enjoy without fear the functional and aesthetic beauty of these wonderful creatures.
Description-Small to medium sized (up to 2” long, roughly half body [carapace and mesosoma] and half tail [metasoma and venom bulb]), mostly dark scorpion with (usually) lighter colored legs; front of carapace is indented; y-shaped, dotted keel on the bottom (although with the stinger ‘cocked’ it becomes the top) of the last segment (segment 5) before the venomous bulb (telson); 3 lateral eyes on each side of carapace; middle lamellae of pectines numbering 6.
Similar species–Uroctonus glimmei lacks forked keel on segment 5, and the tail is noticeably longer than the body; Paruroctonus sp. have bulging or flat front of carapace; Hadrurus obscurus is much larger and has more hair; Anuroctonus sp. have 4 lateral eyes on each side of carapace.
Habitat– Moist to mesic forests and woodlands, up to 5,000’ elevation in nw California; almost always under cover in daylight hours, and seems to prefer wood, rather than rock, for its cover.
Range-West Coast of US; found in the middle and western Columbia River Gorge and north to the south side of Mt. St. Helens (the ones near Mt. St. Helens appear to be the northern extent of this species known range), along the west slope of the Cascades in Oregon up to about 3,000’ elevation, throughout the Siskiyou and Klamath Mtns, throughout sw Oregon/nw California and along the coast from Coos Bay, Oregon to Santa Cruz, California; also found in the western foothills of the Sierras.
Eats-Young ones (1st, 2nd, 3rd instar) tend to choose soft bodied prey like grubs and termites; older immatures and adults feed on spiders, grasshoppers, crickets, beetles, stinkbugs, and most anything else they can subdue.
Eaten by-Snakes, lizards, insectivorous mammals, Jerusalem crickets (genus Ammopelmatus), possibly owls; ETA- my friend Kristi DuBois tipped me off that they may be consumed by pallid bats (Antrozous pallidus), who occupy some of the same range, and are known to prey on Arizona bark scorpions.
Adults active-Year around, but much less active during coldest months.
Life cycle-Probably mate in late spring/early summer; females give live birth (in mid to late summer) to 20-40 young, who are encased in a membrane that the mother helps them tear through before they climb onto her back, where they ride until their first moult; 7 instars and 2-3 years to sexual maturity
Etymology of names–Uroctonus is from the Greek words for ‘tail killer’, which would refer to the venom injecting telson. The specific epithet mordax seems to be from the Latin words for ‘biting/corrosive/pungent, and Dupre (2016) indicates that it refers to stinging with the telson.