Entomology (Study of Bugs)/mass spider drowning


Drowned Spider 1
Drowned Spider 1  
Drowned Spider 2
Drowned Spider 2  
QUESTION: 9/26/14 Friday afternoon I went out to my garden to do some watering.  I noticed that there were (10) spiders, all the same type, completely submerged in the outdoor water bowl.  I change this water almost daily and put a large stick in it in case little critters fall in and need to climb out.  Why would all these spiders climb in to the bowl at the same time and remain on the bottom of the bowl?  I have never seen anything like this.  All the spiders had a swollen sac-like appendage at the back of its body. I didn't know if it was where the web came from or babies?  I ran to my computer and read that sometimes spiders can survive being drowned, so I ran back out and emptied the bowl and laid out the spiders on a board to dry out.  Sure enough, I noticed one of them moving within an hour, and by morning, all but (1) spider had recovered.  I am photographing the one who did not recover and sending it so maybe you could identify it?  I also notice just a little movement in a leg so I am taking him back outside to recover on the grass, if it is even possible at this point.  I just found this all very unusual and never saw so many spiders of one type drowned at the same time.  It seems like they would have been able to climb out, but why so many all at the same time.  The water bowl is for raccoon, squirrel, and possum that pass through.  Thank you for any input you may have.

ANSWER: Belinda:

I grew up in Oregon, so I am familiar with this...Thanks for including the images.

The spiders are all male "folding-door spiders," related distantly to trapdoor spiders and tarantulas.  Here's more about them:


Females and immature males live in silk-lined burrows with an above-ground turret of camouflaged silk, two sides of which can be drawn in to close the burrow.

Mature males wander in search of females at this time of year.

Yes, these spiders can recover from apparent drowning, but I also wonder if birds might have claimed some of the ones that you thought just wandered off.


---------- FOLLOW-UP ----------

QUESTION: Thank you for identifying these spiders for me.  I don't believe that any birds took the recovering spiders, but it is possible.  It was evening and the spiders were still recovering when we checked. They were still there after dark.

I am perplexed what would draw so many of these spiders into the water on the same night.  Any thoughts?  Is this a common phenomena? They were all on the bottom of the bowl and it seems that they could have gotten out.

I found another spider the next night.  It was strange that there were so many on the previous night.  I've never seen anything like it.

Thank you.


Early morning (dawn) is when the birds would have found them, if that is what happened....

These can be abundant spiders, and often locally common, in small "colonies," so this is not an unusual phenomenon at all.  They were not attracted to the water, but simply fell into the dish in the course of their wanderings.  They are not as light and agile as, say, wolf spiders, so they cannot easily extricate themselves from such predicaments.


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Eric R. Eaton


I answer insect and spider identification questions ONLY. Attach images if possible. No "what bit me?", "what do I feed this bug in captivity?", or science fair project questions please. NO TECHNICAL QUESTIONS ABOUT INSECT PHYSIOLOGY.


Principal author, Kaufman Field Guide to Insects of North America. Professional entomologist employed previously at University of Massachusetts, Chase Studio, Inc., and Cincinnati Zoo; contract work for West Virginia Department of Natural Resources, Smithsonian Institution, and Portland (Oregon) State University.

Author, Kaufman Field Guide to Insects of North America, Missouri Conservationist magazine, Ranger Rick, Birds & Blooms, Timeline (journal of the Ohio Historical Society). I have contributed to several books as well.

Oregon State University, undergraduate major in entomology, did not receive degree.

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One of the top 50 experts in all categories for AllExperts.com, 2009.

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Principal author of the Kaufman Field Guide to Insects of North America, Smithsonian Institution (contract), Cincinnati Zoo (employer), Portland State University (contract), Chase Studio, Inc (employer), Arkansas Museum of Discovery (guest speaker). Currently seeking speaking engagements, leadership roles at nature festivals, workshops, and ecotours.

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