Do spiders get sick?

Considering our current events, I thought this might be an interesting topic, although a good suggestion from my sister, “Do spiders poop?” is definitely something blog-able in the near future. These two topics may overlap on some level. I’ve witnessed a lot of spider deaths of various causes and sometimes spider poop is the last thing that happens. So, do spiders get sick? The short answer is yes.

A spider hosting a parasite – probably a larval wasp.

A “sick” spider could mean a lot of different things; a parasite, getting stuck in exuvium (aka molt), pesticides, nematodes, fungi, bacteria, and simply not getting enough water (or too much). I can’t imagine they get sick and contagious like we do. Our physiology is so different. For instance, they can’t sneeze or cough. It’s conceivable that spiders could dine upon a diseased grasshopper and get infected that way. Most spiders self-isolate by nature so if there was ever a spider pandemic, most would probably ride it out with no issue. There ARE such things as social spiders which congregate in large, combined webs. A paper by F. Vollrath in 1986 eluded toward a social spider epidemic affecting a colony of spiders he was studying. He writes, “It is conceivable that a virus had spread and contaminated all or most colonies” but it wasn’t the paper’s focus. It was only mentioned as a heads up for interpreting the data. The outcome was many “dead and sickly” spiders in the web while the healthy spiders evacuated. I did find a few other research papers that warned about or mentioned the possibility of bacterial infections and viruses in spiders, but nothing accessible about the signs and symptoms although they must exist (there is a whole field of invertebrate pathology that I did not delve into for fear I’d never come back). When we see a dead spider, it just looks dead! We can guess the cause, but do we really know?

A dead Agelenid (funnel web weaver) spider that most likely lived a full, productive life judging by its egg sac.

My experience with sick spiders has been noticing changes in their mobility and behavior and just knowing something ain’t right. They look “wonky” which is a word I use a lot in my journal to describe how a spider’s legs won’t extend out all the way. Imagine “Thing” from the Addams Family walking on its first finger joints instead of its fingertips. Wonky is like that. Usually, wonkiness is caused by dehydration and can be quickly remedied with water. Sometimes, it signals the spider’s last moments whether it is old age or something we can’t see happening inside of it. I have a few stories about the weird things I observed that, to me, would define a sick spider.

Artemis, a wolf spider that developed a white blotch on her abdomen.

Case 1: Artemis. Back in 2013, I had a female wolf spider, Artemis (Tigrosa genus), that developed a white splotch on her abdomen. I guessed it to be spider poop, but normally, spider poop shoots out like a squirt gun or drops straight down, so why would it be on her like that? Was she up against the side of the enclosure when she was poopin’ or what? She was kept in a mesh-top enclosure with plenty of air circulation so I ruled out a fungus. I posted to the spiders.us forum to see if anyone else had seen this before and no one had. Other weird things were happening with her. I noticed one of her legs was looking stiff and not flexing when she was moving around. During a check in, I found her self-amputating (autospasy) that leg (it’s missing in the photo). THAT was interesting! Normally, as a result of being enclosed in a cage, she would leave a build up of dragline silk while she traveled the perimeter of the enclosure. I was changing out the substrate every few days to make sure everything was clean and there’d always be more dragline silk, but on the last substrate change, days went by and there was no silk. She died a few weeks later. I’m guessing old age? She died in early autumn and I assume she was full grown when I caught her (no notes on when, DOH!). Wolf spiders can live for eighteen months with two winters under their belts. Maybe this was her second round. Can internal systems in an old spider start to deteriorate?

Case 2: Abdomen bulge Rapidosa. That same year, I collected two more wolf spiders that I guessed were in the Rabidosa genus. Both were full grown females. One died about a month later (no idea why), but the other lived into November producing a blueish egg sac that she toted around until December. Then it disappeared. I’m guessing she ate it. She produced a viable egg sac later that month and carried it until the eggs hatched in mid January. She towed the spiderlings on her back until they dispersed (and I rehoused them) and continued eating as usual until February. Normally, wolf spiders would be overwintering at this time of year. Since she was a mated adult going into winter (as opposed to an unmated subadult) she was old for a wolf spider. But what happened was odd.

Rabidosa momma with spiderlings looking healthy!

I don’t know if any of this was related, if it was old-timer spider stuff, if the humidity level was too high in her enclosure or what, but I noticed the back of her abdomen was dark and the last segment, the tarsus, of one of her rear legs was stuck in a bent position – what’s with stiff leg joints in old wolf spiders? Her spinnerets were flared out instead of tapering together. Her behavior changed, too. When she was healthy, if I bumped the cage by accident, she would move. Now she would be still when I bumped it. When I gently tapped her with a pencil she would suddenly sprint across the cage all crazy, at one point trying to climb UP the pencil! I tried adjusting air flow into her cage. Two days later, the dark spot on her abdomen was a bulge and there was no movement at the joint halfway up her frozen leg. Her spinnerets were still protruding but not splayed out as before. Her movement was lethargic on her last day. She flipped onto her back trying to run from a spritz of water and was very slow to right herself. She died moments later. Internally, the swollen spot on her abdomen is where the cloaca would be, part of her excretory system. Maybe something was blocked?

Case 3: Brown recluse spiderling. Here’s one that has nothing to do with spider old age. I have brown recluse spiderlings from an egg sac I collected over a year ago. I’ve been rearing them for educational purposes. Not a lot of people around Pittsburgh have ever seen one in person. It’s a great conversation starter when I bring them to presentations! I began with over twenty spiderlings and was down to four at this time. Now, I’m at two. In my journal, I’d note when each of them died and I’d pop ’em under the scope to see of I could tell why. Half of the time, they died because of a bad molt, and the other half of the time, they were just dead for no apparent reason. This last one, #12, actually had something odd when I looked under the scope.

#12, a 5th instar (meaning 5 molts ~2 more to go til maturity) Brown Recluse with odd discoloration on cephalothorax.

The dark brown splotch you see is not normal. It’s something internal near where the spider’s sucking stomach and associated muscles would be. Judging by the shriveled abdomen, #12 wasn’t eating either. Spiders not eating isn’t a good indicator for sickness since they can go for long periods of time without doing so and be fine, but this looked like something for sure, although I can only postulate this could’ve contributed to cause of death. #12 was always larger than the other spiderlings and seemingly healthy…

Okay, I gotta bring this back up and end on a positive note. I can reassure you that spiders do not spread infection or disease. A bite may lead to a secondary bacterial infection (if you are actually ever bitten by a spider), but you don’t have to worry about West Nile virus or malaria like with those pesky mosquitoes. I have successfully saved sick spiders that were stuck indoors and severely dehydrated. At work, I’m the spider rescuer. A spider will be hobbling across the floor and I’ll scoop it up in a container, add a few drops of water, and amaze my colleagues who ask, “How did you know it was thirsty?” to which I answer, “It was all wonky.” They really don’t know what I’m talking about, but they seem to be fascinated at seeing a spider drink and get itself right again. Now that we’re all working from home, I wonder if anyone has tried it.

Pretty female Castianeira species (ant-like runners) rescued in teacher’s lounge in Nov., nursed back to health, photographed, and released!

Broadley, Hannah. Insects Get Sick Too: The Study of Insect Pathology. That’s Life [Science]Website. http://thatslifesci.com.s3-website-us-east-1.amazonaws.com/2016-11-10-Insects-Get-Sick-Too-Broadley/. Updated Nov. 10, 2016. Accessed March 29, 2020.

Schultz, Stanley A. and Marguerite J. Shultz. The Tarantula Keeper’s Guide. Hauppauge, New York: Barron’s Educational Series, Inc. 1998.

Trevor Zachariah, Mark A. Mitchell, Manual of Exotic Pet Practice, 2009. Chapter excerpt on arachnids via ScienceDirect.com. https://www.sciencedirect.com/topics/immunology-and-microbiology/arachnid. Accessed March 29, 2020.

Vollrath, F. 1986, Environment, reproduction and the sex ratio of the social spider Anelosimus eximius (Araneae, Theridiidae). J. Arachnol., 14 :267-281 .

Whitcomb, W. H. and Eason, Ruth Robinson (1965) “Rearing of Wolf and Lynx Spiders in the Laboratory (Families Lycosidae and Oxyopidae: Araneida),” Journal of the Arkansas Academy of Science: Vol. 19 , Article 6.

6 thoughts on “Do spiders get sick?

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  1. Thanks, Amy! I so enjoy your posts. Hope you are safe and healthy…you are too close to the hotspots for my comfort. I worry for you. Here in Ohio, we have wine with Dewine at 2 every day 😉 I have to say, even tho he’s republican, he is kickin’ ass in the Corona arena. Dr Amy Acton is a Godsend. So calm and well spoken. Check them out if you haven’t already. Peace, Frances

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  2. Amy, thanks for this interesting post. You are correct that we need more research into spider diseases, but it is a tough subject, since many of the reports are individual incidents, thus anecdotal. There are a number of parasitic fungi that are well known arthropod killers, such as Cordyceps which is one of the brain-behavior pathogens that causes the victim to climb to the top of a branch or whatever before it dies, then grows a spore-bearing structure from the corpse, all the better to spread the spores! (do a search on Cordyceps and you will be amazed) I used to try and keep scorpions in captivity for behavior experiments, and occasionally they would develop a bacterial infection that manifested itself by dark areas near the joints, and was eventually fatal. Other scorpion workers have mentioned the same disease. One hypothesis is that it is a result of keeping arid-zone animals in overly humid containers.

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    1. You’re welcome, Rich! I always end up with more questions than I start with. I failed to include Cordyceps! Thank you for mentioning! It is creepy and amazing! I’m curious about your scorpion observations – dark areas near the joints…interesting. Are there any publications about that I could check out? I always appreciate your feedback! Stay well!

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  3. Thanks for a website celebrating spiders instead of promoting fear. I live in the desert SW and have free range wolf spiders in the house. They’re quiet, clean and attractive. Found your site looking up Sick Spider as I have a droopy (wonky) one today. Everything droops! Unfortunately legs starting to curl up so I’m afraid its a goner, always sad. I believe they are happy in the house or id put them outside. Should I?

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    1. You are welcome! I would think they’d be happier outside. If you have them free ranging in the house, the indoor habitat may be working for them if there’s a food supply of some sort. Did you offer a drop of water to the spider? I’d think a native to the desert wouldn’t be as susceptible to desiccation? Thank you for being a spider advocate and sharing your interest!

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