Mud Daubers in Spider Room....

[Little Grey Spider]

I've found two mud daubers in my spider room in as many days. I had a good chance to observe the second one after releasing it outside. I believe it's Sceliphron caementarium which in my little bit of research is said to be a solitary creature and that puzzles me since I've had two individuals in the same room in two days. My research further indicated that these are spider killers in my spider room! I tried to find how they hunt but could find nothing. How do they find the spiders to pack the cells of their nests? Are my spiders attracting them somehow? I can't think of a way how except perhaps with their excrement? My pinktoes do poo a lot. But anyway, I was just curious for more info in these giants. It was quite docile during the catch and release- I thought perhaps it was lethargic but later read that that is their nature. Just looking for some insight on the invaders. Thanks in advance!

 

[The Snark]

I've watched the wasps hunting. Flying low, a foot or two above likely spider areas like detritus. Always has stuck me they have highly developed eyesight. Probably a genetically written profile in their brains they reference to. But how they have located and homed in on a room with spiders, that is a serious mystery needing solving.

 

[Dennis Nedry]

But how they have located and homed in on a room with spiders, that is a serious mystery needing solving.

Scent maybe? I've seen a spider wasp sticking it's nose in the gap of a car side mirror, later found out there was a huntsman hiding in there. No way it could've seen the huntsman while flying around

 

[The Snark]

Scent maybe?

Quite possibly. On one hand, it is extremely difficult if not impossible to determine the olfactory abilities of invertebrates, but on the other hand, taking the evolutionary timeline into account, the probability of such senses being highly refined is quite high.

 

[Galapoheros]

My guess is that it's mostly visual and they have an instinct about where to look. When I was a kid I broke open the nests and noticed mostly crab spiders. They may pick up on eye shine or quick movements that have "that pattern" and look to it. I've thought they aren't very defensive because they aren't communal and they make a nest that is very protective, so they don't have to be. Do you have a pic of one of them?

 

[myrmecophile]

I suspect that prey is a seasonal thing. In years when orb weavers are prevalent all the nests I broke open were filled exclusively with them, at other times it was all jumpers. I agree that they are probably picking up cues. In my experience though they do not hunt indoors, but often come indoors with the intent of building a nest. In my neck of the woods indoor nests are exceptionally common to the point of being pests.

 

[Little Grey Spider]

My guess is that it's mostly visual and they have an instinct about where to look. When I was a kid I broke open the nests and noticed mostly crab spiders. They may pick up on eye shine or quick movements that have "that pattern" and look to it. I've thought they aren't very defensive because they aren't communal and they make a nest that is very protective, so they don't have to be. Do you have a pic of one of them?

I don't, but I got a very good look at the second one. Sadly, the first one got murdered. The second one I took care of- I was terrified. But I watched it for a few minutes and coaxed it into a cup. Then when I put it outside it hung around for a few minutes so I got a decent chance to look so I'm fairly confident on ID.

 

[Little Grey Spider]

I've watched the wasps hunting. Flying low, a foot or two above likely spider areas like detritus. Always has stuck me they have highly developed eyesight. Probably a genetically written profile in their brains they reference to. But how they have located and homed in on a room with spiders, that is a serious mystery needing solving.

I agree. It was only two, but it seems like that is bordering on more than coincidence. A couple of scenarios I've been trying to think of are they are attracted somehow (e.g. like I mention the spider waste before) Or maybe it's something as simple as these are emerging from a nest that could've been built in my wall or window so they're coming out but are inside the house? I don't see anything abnormal, but my house is almost 150 years old, so there are plenty of hiding places for critters. I'll let you guys know if I find another and I'll definitely snap a picture next time. If there is a next time.

 

[Little Grey Spider]

I suspect that prey is a seasonal thing. In years when orb weavers are prevalent all the nests I broke open were filled exclusively with them, at other times it was all jumpers. I agree that they are probably picking up cues. In my experience though they do not hunt indoors, but often come indoors with the intent of building a nest. In my neck of the woods indoor nests are exceptionally common to the point of being pests.

oddly enough, my yard is usually FULL of spiders- usually P. undatus, L. venusta and A. diadematus. I've seen the odd individual here and there, but the numbers have seriously gone down this year. I wonder if the wasps have anything to do with it? Or the weird winter we had. Who knows?

 

[The Snark]

And then the elephant in the room, why spiders? Wasps are day hunters, spiders are more active at night. Also, there are zillions of other invertebrates to pick on.

 

[Salmonsaladsandwich]

And then the elephant in the room, why spiders? Wasps are day hunters, spiders are more active at night. Also, there are zillions of other invertebrates to pick on.

Spiders are abundant, soft- bodied and nutritious. They can't fly and usually have no physical defenses apart from biting, which the wasps are skilled at avoiding. Off the top of my head there are other solitary wasps that provision their nests with crickets, katydids, cockroaches, mantids, caterpillars, cicadas, honeybees, flies and scarab beetle larvae. Some wasps had to take up hunting spiders, and it happens that spiders are a good enough food source mud daubers and pompiliids are rather successful.

It might actually be more advantageous to hunt spiders when they aren't active. That way, the spider may be less likely immediately attack when confronted by the wasp, instead trying to remain hidden.

At the same time, both from what people have said here and images showing the contents of mud dauber nests, it seems they have a preference for crab spiders, jumping spiders and orbweavers. Jumpers are diurnal, crab spiders sit on flowers during the day (where the wasps can encounter them while feeding on nectar) and orbweavers usually hide in small small shelters near their webs. It's probably a lot easier for a wasp to catch an orbweaver hiding in a rolled up leaf than one sitting in the center of its web.

 

[The Snark]

It's perplexing, around here anyway. I unhesitatingly crack open mud dauber nests and it's always a spider inside and we are talking a LOT of nests. When I finally sold my jeep I cleaned it thoroughly, finding about 30 old and new dauber glops. (The view under the dashboard was positively arachnid Orwellian).
Caterpillars around here and far more abundant than spiders, but with a drawback. Plump, juicy, and very often lethal; apparently their day glow ultra obvious warning colorations have sent the signal down through genetics for all predators to avoid them.
And it is always the smaller spiders, mostly Lycos and Huntsmen here. Opportunity targets out during the day for one reason or another. Our hefty Minax are avoided, only leaving the burrows at night. There are undoubtedly mentally defective wasps that would attempt to take them down like the T Hawk but no.
Perplexing.

 

[Darktiger432]

My parents had a loafing shed filled with spiders early summer last year. Then swarm of European paper wasp later that summer. But It was crazy how many there was. But they ate up all those spider. Up to last year I thought the wernt carnivereous. After that I saw videos of wasp taking apart a dragonfly.