The Backyard Arthropod Project

Kitchen linoleum is a great place to find spiders - they stand out so well, particularly on light-colored floors, and usually they are far enough away from cover that catching them is a snap[1]. This fellow was scurrying across the floor, and once I caught him, he kind of scrunched up with his legs pulled in:

“Hey, wait”, I hear you cry, “what makes you think this is a male, anyway?” Well, if you look at the end of his abdomen, you can see some pretty prominent projections, these are the spinneretes. Prominent spinneretes like this are a feature of funnel-web-weaver spiders, family Agelenidae [7]. For most of these spiders, the females build characteristic funnel-shaped webs, which they rarely leave, while the males spend a lot of their time wandering around looking for love. This one was wandering, and is therefore probably male.

After a bit, he unscrunched his legs some so that his body was a bit more visible, but this didn’t help much - he’s nearly black, with not much in the way of distinctive patterning:

He’s also missing a leg. So far, I think every spider I’ve posted pictures of has been missing a leg. They must lose them at the drop of a hat. Of course, if you have 8, losing two or three is probably not a big deal.

I tried to get a picture of his eyes, with not too much success, but it looks like there are two parallel rows of four eyes each, all pretty equally sized and none all that large. Again, this is characteristic of funnel-web-weavers.

More to the point, it is not characteristic of wolf spiders (family Lycosidae), which have two enlarged eyes that are pretty distinctive.

So, I’m not going to get much of an ID on this one, from the looks of things. We’ve got it down to the family, anyway, which is something.

In the course of trying to identify it, I found this page at Transylvania University[2], which has a little menu-driven system that claims to identify your spider. The thing is, I went through their questions, and it came back with the claim that I had something in the genus Loxosceles. That is the genus the infamous Brown Recluse belongs to. OK, now, right away I know this is wrong, because (a) my specimen doesn’t really look like the pictures, and (b) the Brown Recluse and its relatives don’t live this far north in any case (as can be seen from the range map on the Bug Guide page). Granted, the site with this ID key is in Kentucky, where Brown Recluse spiders do live, so for them it would be a possible ID, but I think they are being needlessly alarmist[3].

Which brings me to a point: this little spider fella is exactly the sort of thing that people see running around the house, and they immediately freak out, because they’ve been told over and over again that spider bites are dangerous. Then they squash the poor guy, whose only crime is looking for love in the wrong place [4]. This whole thing about spider bites is almost completely out of hand. Somebody sees a spider and the first thing they think is, “Is it poisonous?” And every largeish, brown spider is a “Brown Recluse”, and is going to bite you. There is even a whole song-and-dance about how spider bites turn into these massive, necrotic lesions, where the skin in the middle dies and sloughs away, and they never heal, and you lose body parts, and all that jazz.

From what I’ve read, one shouldn’t be too quick to blame these lesions on spider bites, unless you actually see the spider biting you (or feel the bite and actually see the associated spider or its corpse shortly afterwards). There is a nice article by a couple of Canadian entomologists explaining how people all over the world are convinced that necrotic lesions come from spider bites, even though the vast majority of the time they are caused by things like bacterial skin infections. There’s apparently a lot of people in Canada who claim to have been bitten by brown recluse spiders, even though these spiders have never actually been found in Canada.

A big problem with spider bite diagnoses is that, mostly, they are made on the basis of “I have this injury that looks like a bite, and there are spiders in my bedroom”. Given how many other things exist that bite people (mosquitos, black flies, biting flies, bedbugs, fleas, chiggers, ticks, lice, certain types of assassin bugs . . . not to mention simple pimples, ingrown hairs, splinters, infected thorn wounds, you name it), pinning it on some hapless spider just because it happens to be around is kind of gratuitous.

I’ve never been bitten by a spider, and it sure isn’t for lack of opportunity (I obviously regularly poke, prod, and pick up large spiders that I find around the place). I once asked over 200 people on an email mailing list if anybody had ever seen a spider actually in the act of biting them (or scurrying away from a bite), and exactly two could honestly confirm a bite. Both had been bitten on the hand while unstacking firewood, by some “large, grey, flat spider”, and both said the bite was minor, less serious than a wasp sting, and cleared up quickly with no lasting wound.

I think that spiders are getting a bad rap for very little cause, and we really shouldn’t blame them for a bite unless it is a sure thing. Especially those of us up here in the “frozen north”, where venomousness does not seem to be something that comes up a lot.

Which brings up another thing: Why is Michigan, most of the northern tier of US states, and Canada so short of venomous creatures? Aside from a few species of wasps and bees[5], and one species of very small rattlesnake, there’s nothing in Michigan. Not like, say, Australia, which I understand has about half of the world’s species of poisonous snakes, a bunch of pretty toxic spiders and other arthropods, ocean reef fish with poisoned spines that will kill you, and even a venomous mammal[6], for crying out loud.

I don’t know the reason for this, but I have a theory: I think it depends on what your greatest enemy is, how fast you can breed, and how long you have had to evolve defenses. In Australia, the greatest enemies are the other animals. Food is scarce, so it’s hard to have lots of offspring. In that sort of environment, the best way to survive is to be able to quickly kill anything stupid enough to attack you. Even though making poison has a significant metabolic cost, and requires you to come up with a way to keep from being killed by your own poison, even a so-so poison is great for killing or driving off unprepared predators. This works for a while, but over time the attackers who don’t die are selected for, and their offspring can tolerate your poison. So, your descendents have to evolve poison that keeps getting nastier and nastier. Finally, if allowed to evolve undisturbed long enough (like Australia was), you get all these fantastically toxic animals, with poisons that get written up in the Guinness Book of World Records as “most toxic chemical known” or something.

Meanwhile, in northern North America, the glaciers have just pulled out, and the plants and animals moved into the pristine new area. Here, the enemy is not the other animals - the enemy is Winter. Winter will kill you no matter how poisonous you are, so making poison is a needless diversion of your metabolism from the things you really need. Things like blood antifreeze so ice crystals don’t rupture your cells when it gets to -40 degrees. Or the ability to lay a few tens of thousands of eggs in the fall so that at least a few will be able to hatch out in the spring. Or the ability to dig several feet down, below the frost line, and enough fat reserves to hang on down there until it warms up again. Then when spring comes, the survivors of Winter suddenly get this huge flush of food, letting them breed and spread and eat, and there is so much to eat that there isn’t that much predator pressure on them, personally, so venomousness doesn’t really protect them that much. And, they can eat and breed so fast that no predator can catch all their offspring, so it still isn’t really worth it to divert resources to venom. So, on the whole, most animals don’t bother with defensive venom, because there’s no percentage in it.

Keep in mind, though, that even in Australia (”The Venomous Continent”), hardly anybody dies from the bites of venomous animals, especially if they have the sense not to go around sticking their hands into dark crevices. Here in northern Michigan, venomous arthropod bites are so far down the scale of likelihood that it isn’t even worth taking seriously. If it wasn’t for the occasional person that goes into anaphylactic shock from wasp stings, it wouldn’t be a concern at all.

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[1] A good way to catch spiders (and lots of other kinds of insects ) off of the floor or window is with a mason jar and a playing card. Just invert the jar, put it over whatever you are trying to catch, and then slowly slide the card under the jar, giving them time to climb off the floor/window and onto the card. Then just turn the whole thing over, rap the card to knock your captive into the bottom of the jar, and quickly put on the lid. Easy!

[2] No, not that Transylvania University. This one is in Lexington, Kentucky. We actually saw the campus once, it’s just your standard liberal arts university. Kind of a shame that they don’t play up the name more, but I guess that isn’t the image they want to project.

[3] Besides, I think their ID menus are broken, because I specifically said that my specimen had 8 eyes, but they still came back with the Loxosceles ID even though Loxosceles only have 6 eyes.

[4] And if, by some chance, they try to ID it after the fact from his poor, squashed corpse, sites like the one at Transylvania U. tells them that this harmless little spider was dangerous!

[5] And a lot of those are recent imports. Honeybees and European Paper Wasps both came from Europe.

[6] For anybody wondering, the mammal is the platypus. The males have a poison spur on each of their hind legs. They mostly use this to fight with each other, but I expect they’d stab you with it too if you messed with them.

[7] I should point out that the funnel-web weavers in North America are no relation to the Australian funnel-web spiders. They are entirely different groups of spiders that both happened to develop similar styles of webs. The species in North America are certainly not dangerous.

Other articles related to this topic:

• Female Crab Spider
• Jumping Spider
• European House Spider, Cluster Fly
• Male Goldenrod Crab Spider
• Thread-legged Bug