Wednesday, August 11, 2010

Wasp Wednesday: Blue Mud Dauber

Among insect architects, the Blue Mud Dauber, Chalybion californicum, is not Frank Lloyd Wright. What it does have going for it is a remodeling career. Oh, and a reputation as a fierce enemy of black widow spiders.

Blue mud daubers are solitary wasps in the family Sphecidae. Females take over abandoned nests of their cousin, the Black and Yellow Mud Dauber, Sceliphron caementarium. While Sceliphron gathers mud to make her nest, Chalybion carries water to an old nest to soften it and remold it to her needs. The result is a very lumpy version of the normally smooth Sceliphron nest.

Chalybion makes up for any engineering deficiencies with a persistent, clever, and energetic approach to catching prey. The female wasp is able to land on a spider web without getting entangled, then do a convincing impression of an insect that is in distress. She plucks the web and draws the spider out. The poor arachnid comes dashing down a thread expecting dinner and instead seals its own doom. The blue mud dauber stings the spider into paralysis and flies it off to her nest.

Among the known spider hosts for the blue mud dauber are black widows, specifically the Southern Black Widow, Latrodectus mactans. For a highly entertaining account of this I recommend chapter five (“The Terrible Falcons of the Grassland”) in Hunting Big Game in the City Parks, by Howard G. Smith (New York: Abington Press, 1969). Additional spider hosts include mostly other cobweb weavers, family Theridiidae, small orb weavers (Araneidae), and the odd lynx spider (Oxyopidae), crab spider (Thomisidae), or jumping spider (Salticidae).

Mud daubers in general stuff a multitude of spider victims into each mud cell before finally sealing it with a curtain of mud. A single egg had been laid on the very first spider stored at the bottom of the cell. The wasp larva that hatches then gradually consumes all the spiders, leaving a smattering of legs as the only indication there was ever anything else in there with them. The mature larva then spins a papery silken cocoon inside which it pupates. A few weeks later (or come spring if it was overwintering) an adult wasp chews a round hole in the end of the cell and exits. Holes in any other part of the mud nest indicate that some kind of wasp parasite chewed its way to freedom instead of the mud dauber.

Male mud daubers are far less industrious than their female counterparts. Their sole mission is to father the next generation. Meanwhile, they are content to sip nectar from flowers or extrafloral nectarines. They also like oozing sap from wounded trees and, perhaps most of all, the “honeydew” secreted by aphids and scale insects. Both genders of mud daubers like this delicacy, which is nothing more than the sugary liquid waste produced by those sap-sucking buggers.

Meanwhile, after a heavy day of drinking, males may gather in “bachelor parties” to sleep it off during the night. These congregations of normally solitary wasps can cause a bit of anxiety in people who confront them. Take a look at this image and comment thread for an example.

It should be noted that there are actually two species of Chalybion found north of Mexico. C. californicum is transcontinental in the U.S. and southern Canada, while C. zimmermanni ranges from Tennessee and North Carolina south to Florida and west to Texas, Arizona, and into Utah. I am curious as to whether the males I photographed recently in southern Arizona are C. zimmermanni given the smoky, rather than violaceous, wing coloration (see below).

Enjoy making your own observations of these wasps. They are not the least bit aggressive and, because they often nest on the exterior of buildings, are easy to watch.

Sources:
Bohart, R. M. and A. S. Menke. 1976. Sphecid Wasps of the World. Berkeley: Universithy of California Press. 695 pp.
Krombein, Karl V. et al. 1979. Catalog of Hymenoptera in America North of Mexico. Washington, DC: Smithsonian Institution Press. Vol. 2, pp 1199-2209.

101 comments:

  1. I have found a coccon in a mud nest and wondered about it.

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  2. So, can I safely assume that the single-tube mud-dauber nest that we found partially constructed in our barbecue grill in northern Michigan was most likely the black-and-yellow mud dauber, because it was being newly constructed? Or will the blue mud daubers build new nests themselves if they have to?

    Incidentally, it was stocked with four yellow crab spiders, not cobweb-weavers.

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    1. I have been watching a dark brilliant blue mud dauber build an entire organpipe nest. I was surprised to see all the web sites say the same thing "she steals nests". I have witnesses! She buzzes and spits the mud she gathers along edge to edge, now she is bringing food back and forth. She buzzes around me a lot then off to her nest.

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    2. Anonymous, you are describing another species entirely: Trypoxylon politum, the Pipe Organ Mud Dauber. The Blue Mud Dauber does not "steal" nests, she simply re-uses old, abandoned nests of the Black & Yellow Mud Dauber.

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    3. Are these blue winged wasps carpenter bees and do they harm your wood deck.

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    4. Please read the blog post. "No" and "no" to answer your questions.

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  3. Tceisele: Yes, your are correct. Also, blue mud daubers will *not* construct their own nests. At least this species seems incapable of starting from scratch. Other species of Chalybion elsewhere in the world nest in pre-existing cavities like hollow stems that they then partition with mud into a linear row of cells.

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  4. Any idea what insect (if not a wasp) will build a multi-chambered nest with tiny stones? Cavity opening = ~ 3/16"Location: north Chihuahua Desert near Terlingua, Texas.
    Resembles mud dauber nest, but is constructed of tiny stones.

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  5. Macrobe: Sounds like one of the "resin bees," family Megachilidae, but I'm only familiar with single-chamber nests. Otherwise, your description fits their nests perfectly.

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  6. Thanks for helping us identify our insects! We have about 40 - 50 if these congregating on a hanging plant at night, and couldn't reconcile the "solitary wasp" description with this behavior. Now we know!

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    1. @Cynthia - we also have a lot of these guys in our hanging (and flowering) succulents. It gave us quite a scare. How did you handle the situation?

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  7. Glad I could help, Cynthia :-) Thanks for the compliments!

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  8. I live in southern Ontario,Canada and have never seen these until today and I've seen several flying around all in one day - not sleeping as described. Why would a solitary wasp be so plentiful all of the sudden?? They are freaking me out! :-P

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  9. CA: I don't know how to answer that, but certainly no reason to get freaked out. Solitary wasps are definitely *not* aggressive like social wasps (hornets, yellowjackets, paper wasps). There is no great number of helpless larvae to defend, so females have no reason to "attack."

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  10. So am I safe to assume that these are probably the "nicest" wasps, meaning that you really have to tick them off in order for them to sting you (like bumblebees)?

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  11. Yes, folks, these are solitary wasps that are too busy going about nest-making and hunting to bother stinging you. Further, the males, which *do* often hang out together overnight, have no stingers to begin with. Are we all clear on that, now? Sorry, I apparently didn't make this clear in my story?

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  12. Thanks for this! I am painting the exterior of my house and have encountered some of these and am happy to know they're not aggressive.

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  13. Hi, I just killed a Black Widow in my garage. While researching the BW, I found that Blue Mud Daubers enjoy them. Well, I have lots of Blue Daubers around too. Does this mean I should expect more Black Widows? Do the Blues eat mostly Black Widows? What is the best way to eradicate the Black Widows? Thank you very much for all of the great and fun information!

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  14. Johnny: You should have *fewer* black widows if the wasps are hunting them :-) Very difficult to eradicate widows for several reasons: They effectively hide out of reach of contact insecticides, and the one that is killed is quickly replaced by another. Just be careful not to reach your hands or feet where you can't see, and inspect firewood and other material coming indoors from outside. Thanks for the compliments on the blog posts!

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  15. If I have a bunch of blue mud daubers around my house, does that mean I have a bunch of black widows as well?

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  16. Mackdad: No, you don't necessarily have lots of black widows. The Blue Mud Dauber is largely an opportunistic hunter, so it is taking a variety of different spiders.

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  17. I was always afraid of those blue and black mud daubers. Thanks for clearing it up, I guess I will stop killing them.

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  18. Thank you for reconsidering! Solitary wasps in general (where each female makes her own nest) are pretty harmless. They are too busy doing their thing to bother with people.

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  19. Do these live in Arizona? I just found a metallic blue wasp that appears to be a female, sinve you said males don't have stingers and this one clearly does.

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  20. Yes, they live in Arizona, but so does a larger look-a-like, Chlorion aerarium, that hunts crickets. I did a post on that species, too.

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  21. Great info, I just came across a large group of males hanging out on my deck railing. I was going to kill them, i have a one year old and was worried, but as the males dont have stingers i will let them be.

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  22. That is great to hear, Kris :-)

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  23. Thanks for all the info a great site. I Think What I have are the b/b mud daubers. I do have a lot of spiders in my yard, mostly wolf an red spiders. The only problem is no nest, they hang out under our play set in the back yard. They form this football size body under one of the corners. They have never stung but rather do a mad swarm when you go near. Last year we used your basic wasp killer, after 3 different rounds they were gone. That only lasted about 6 weeks, they came back and lasted till fall. They are back and are starting to grow in numbers. It seemed odd after reading that they would be forming this body of themselves under there. We've lived here for three years an have never seen any indication of a previous nest. Also it is a mix of male an female. Some enlightenment would be wonderful, thanks

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  24. Thank you for the kind compliments. Interesting what you say. I'll have to see if there are exceptions to the bachelor sleeping masses. I can't explain the absence of obvious nests, but I'm sure they must be there somewhere....

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  25. 8JULY12
    I just encountered one of these interesting Blue Wasps hanging on the curtain over our transome window. i hit it with a magazine and captured it and put it in a ziplock bag. It was very much still alive and really ticked off. I have since killed this Wasp using some cleaner and saved it to look up what kind of insect it was. I have only seen one other one in my 43 years. Are they common in the state of Iowa? We live near the Mississippi River. We have been experiencing a severe drought and alot of things in the yard are out of the ordinary. Any comments from you will be helpful. Thanks, Chris Anderson

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  26. Chris Andeerson: Yes, these should be common in Iowa. Sorry to hear you overreacted, though. These are solitary wasps and unless physically molested will not sting you (and the males don't even have stingers). Next time, please consider putting a clear container over the next wasp (or any insect), sliding a card underneath it, and releasing the animal back outdoors. Thank you :-)

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  27. I have these things constantly flying around my front door. They always hit me in the head when I am walking out, and I can't stand it. Perhaps these are a different species as they appear to be quite aggressive?

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  28. Jack: You might be referring to paper wasps. They sometimes smack into mammalian enemies as a warning....Also, insects can be "aggressive" and still be harmless! Please learn to live with the insects around you whenever possible. Thank you.

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  29. Just bought a house and had at least 1 flying around for the first day or two. I found it dead on the kitchen counter, and want to know how to get them back. I have already found three black widows, and I am petrified of spiders, and I have 3 kids and a dog. I figure natured way to help control widows is a pretty good way. Is it possible to purchase, or breed them?

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  30. Levi: There probably is no "getting them back" unless they want to be there. They are not sold commercially as black widow control because they are largely opportunists that will prey upon just about any web-weaving spider. In the meantime, I would teach my children not to reach into places they can't see, be careful of picking up any object that has been outside for awhile, etc. That should go a long way toward minimizing any interactions with widows. Any widow you kill will likely be replaced by another sooner or later because good "web sites" are a scarce commodity.

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  31. Do they live in Ohio. I find several of them in my kids room by the window dead. Now I see one flying around. I'm too afraid to see if it has a stinger or not. They look like the picture provided above( 1st pic) but the color black. I have yet to see a nest.

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    1. Yes, Joanna, they do occur in Ohio, but so do wasps called "grass-carriers" in the genus Isodontia. Those wasps are also solitary, and may nest in the window tracks of homes and other buildings. Neither kind of wasp will sting unless you physically molest a female. Males don't sting; but, stingers are retractable, so you won't see them.

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  32. Well, it's January and there is still a little snow on the ground here in Southern New England. I went to pick some winter greens for my soup and there were several blue wasps hanging around the plants, in the rain. I've never seen them in the winter. Seemed strange so I had to investigate.

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    1. Without seeing specimens, or at least clear images of them, I'd be hard-pressed to know exactly what they are.

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  33. Great information, we enjoyed learning a little more about the insect we found in our garden. Thanks!

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    1. You're very welcome! Thank you for the compliments.

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  34. hi, so i have had honestly a war going on at my house, first i had brown recluse spiders infest my house then house centepedes show up and now these blue mud daupers... with the chain of events taken into effect what can i expect to come next? what preys on these wasps?

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    1. Ryan, with all due respect my mission is to discourage fear and battle mentality and replace it with fascination and appreciation. Solitary wasps are not at all aggressive, and males do not even have stingers. Prevent insects and arachnids and other arthropods from entering your home by sealing cracks and crevices, replacing worn weatherstripping on doors, and mending holes in window screens. Carefully inspect objects you bring inside from outdoors (or neglected storage spaces). That should help considerably.

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  35. i dont want to get rid of the wasps i think they will do my house hold a whole lot of good i was just wondering if there are any specific preditors to the blue mud dauper. so i can atleast prepair myself for the next wave of life that i may be sharing my house with. ive actually had one land on my hand the other day and it was fairly docile this is why im researching what they are.

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  36. I have identified both species of mud daubers flying and entering the door jam in front of my home. I have sprayed a few out of fear, but was wondering if they would/could construct a nest in my attic? My wife wants me to call an exterminator, but I hate spiders and these seem like the kind of guys, or gals, to keep around. Thoughts?

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    1. Mud daubers of all kinds can most definitely nest in attics. However, remember these are solitary wasps that do not behave aggressively. I can't stress that enough. Unless you physically molest a female wasp, she is not going to sting you. Most people object to the nests as eyesores and remove them for that reason. I would not worry. Certainly no call for a pest control service.

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  37. I've seen more of these than I would like the past couple of months. They have gotten into my house and seem to like the light (bulbs, and windows). How can I get rid of them? This is the first I've seen anything like them in South Dakota. Thank you for helping me identify what they are!

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    1. Without seeing specimens, or at least images, I'm hesitant to say they are Blue Mud Daubers....but I would consider them a nuisance at most, and simply usher the "indoor" ones into containers and release them back outside.

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  38. I have a questions. We have a very old home and moved in the middle of winter, so we did not notice any wasps until summer came along. First we saw what seemed like just the regular wasps for Illinois. They were in the attic and windowsills. We removed any nests and had an exterminator come. The past two weeks we found hornets and were able to get rid of them. Now we are finding what seems could be mud daubers or Chlorion aerarium flying around our mailbox in front of our porch. Everytime I try to go near the mailbox the come at me. Could you give me any insite in to which kind of wasp they are? And if there is a way to move them to a different part of the house that is not by the front door.

    Thanks

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    1. Without seeing the wasps, I can't offer an identification, or suggestion for "control." Unless you have an active nest of social wasps (paper wasps or yellowjackets or European Hornet)in extreme proximity to your home, you do NOT need extermination services. Solitary wasps like mud daubers are not aggressive! They may be initially frightened when surprised at your mailbox, but they are flying to flee, not flying at you out of aggression. Unless you physically grab one (and it is a female), you are not going to be stung. Simple as that.

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  39. Howdy Eric, big fan here. We have both kinds of these mud daubers flying around in our barn in northeast Colorado. We have never been stung, but I am constantly bumping into these little guys because they are so thick in the barn. My wife and daughter are terrified of them, and I was wondering if you knew how we can persuade them to move outside. We just want our barn to ourselves. The misses won't help me with the farming as long as they are present. Thanks!

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    1. You would have to "bug-proof" the barn to keep them out, and I have yet to see *any* barn that has tight enough construction to qualify....Unless you physically grab a female (and most of what you are seeing are likely males, which don't have stingers), you are *not* going to get stung. These are not social wasps, so they have no large nest of offspring to defend.

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  40. My 11 year old and I saw several of these today sitting on mint that was flowering. Because they seemed nonagressive we decided to leave them be & enjoy their beauty. I am glad to hear that they are spider hunters (kid loves insects, HATES spiders). We definatly will not be killing these wasps! We did give them a wide berth just to be safe. Thank you so much for the information, you made her day!

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    1. Aw-w-w, you're welcome! Thanks for sharing your discovery.

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  41. Do you know of remedy for sting? I was stung by one of these 2 hours ago and it is still very painful.

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    1. Oh, so sorry to hear that :-( I was out of town and offline when your comment came through, so hope you are feeling much better by now. Different people have different reactions to insect stings because our individual immune system responses differ markedly. Do seek medical attention if you experience severe swelling, difficulty breathing, or elevated heart rate....

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  42. Just wanted to say thank you for this awesome article! You identified my wasp for me, hooray!! :D

    By the way, I mentioned you in the description of my picture, I hope you get some visitors! :)

    http://www.ipernity.com/doc/290645/25832693

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    1. Aw-w-w, happy to help! What an outstanding image on your ipernity page! Thank you for sharing that.

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  43. I hate to say it but my husband killed one of these beauties this morning. Wasn't intentional though. He tried to blow his nose about 3 a.m. and somehow there was one in the tissue. It did sting his top lip which made him automatically kill it. What I am wondering is how they migrated to Iowa when from what I have read they are California natives?

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    1. Amber: No apologies necessary considering the circumstances. I hope your husband recovers quickly....The scientific name, Chalybion californicum, simply refers to the state from which the wasp was first described as a species. It ranges naturally across the entire U.S. and southern Canada.

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  44. I love that you are their voice!! I don't like killing bugs even the ones that freak me out and ones I KNOW will sting or bite me with very serious n painful side effects. I just cant! im a big practitioner of the jar and card relocation procedure as well. I will send you a separate message about a nest of something I can't find info about anywhere. And there are tons of them all over the outside doors and mouldings n such on my moms house in alameda. There are lots of spiders, moths n insects in the area but I'm curious to know who my "neighbors" are. There is one in the front doorway between our screen door and front door! Shall i send you a photo?

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    1. I'd be glad to help. E-mail me with something in the subject line that I'll recognize: BugEric24ATyahooDOTcom.

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  45. We keep finding these in our spare bedroom. The first time there was about 10 or so just laying in the floor dead. A couple of them were still alive, but barely. I keep finding new ones on the floor dead, or barely alive. Could you please give me some information as to what might be going on? I have no clue what to do, or how they even got inside.

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    1. I would have to inspect your home to see how they are getting in. Often, mud daubers in general will nest in the attic, and the next generation that comes out of those nests gets disoriented and ends up flying around indoors. That is my best guess. Why they are dying I have no idea.

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  46. Thank you for this awesome and informative page! My 7 month old likes to hang out on the porch and watch traffic and myself as I do yard work. I noticed I have quite a few of these beauties and the black and yellow daubers using under my porch as a nesting ground and I had become very very nervous about him getting stung. Now with knowing they're nonagressive, I can leave them be and not worry about them hurting my son! I'm happy I don't have to get rid of them, I have noticed the spider population on my porch has decreased drastically since they've shown up and I'm quite happy about that. Hopefully I can get pictures of them to share with you, because they are quite lovely.

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    1. Audrey, thank you for sharing. I live for stories like this :-) At some point I hope to add an interactive forum to this blog.

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  47. Do these insects secrete anything from their back end when they feel they're in danger?

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    1. Not that I am aware of, Ryan. Females have a stinger in their back end, of course. Males may have glandular secretions that help them find congregations where they spend the night.

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  48. Hi, I need to redo the exterior of my house and there are MANY of these that chose to build their home in between the layers of cedar that I have as actual material on my exterior wall. I will have to ''disturb'' them a great deal. They never get close to us and, even though they are maybe hundreds of them, they never bothered us... didn’t even know they could sting till lately... Now that I will need to get real close and also unfortunately destroy some of their nests, I’m really afraid ... do you have any suggestions for me?

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    1. Paul: It should not be an issue. These wasps would rather flee than fight....but if you could wait until after the first frost, then there shouldn't be any live adult wasps to deal with at all. Mostly, I doubt you would have a problem. I can't tell you what *else* might be under those shingles, though.

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    2. Thank you so much for the reply... really appreciated!

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  49. Thanks for a great thread! Based on this discussion I think I have blue mud daubers rather than steel-blue cricket hunters in my yard. For the last couple of years I've had a bunch of Argiope orb-weaver spiders in my garden in the middle of the city. This year they started well, but I haven't seen any in a couple of weeks (mid-August). The metallic blue wasps on my sweet pepperbush may explain it! I do have crickets (fairly unusual in the middle of the city). Sad to miss the spiders but glad my ecosystem is working at several levels!

    L in Somerville

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    1. Thanks for sharing your story! I bet there are still a few Argiope around. The wasps don't get *all* of them.

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  50. For the last 2 to 3 weeks I've had these blue mud dobbers flying just above my yard could you please tell me why there's a lot of them like hundreds of them

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    1. Bo, they could easily be some other kind of wasp, and likely males (which don't sting), looking for females. They could also be females nesting in a dense aggregation (each female still maintaining her own nest), but then you would see them landing and digging. Again, I suspect they are not blue mud daubers, but a different species.

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  51. I've had a lot of blue dirt dobber flying right above my lawn the last 2 to 3 week just wonder why it's a couple hundred just above the grass from morning till about 3 pm?

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  52. Hello Eric! I just wanted to pop by and thank you for this information. I just moved 1200 miles to central Florida and found two of these guys in my bedroom last night. Where I came from wasps are super aggressive and even my cat had enough sense to get away from them. But I was able to scoop both into a bowl and put them outside onto my balcony. They did not get aggitated when I put a bowl over them, nor did they swarm at me when I took the paper off the bowl (though you can bet your socks I shut the screen really quickly just incase!). And they both took their merry time leaving the bowl and just flew off. They were absolutely gorgeous. I do not mind bugs so much, but I was worried about my cat. He is a hunter, albeit a bad one but he has the hunt-play instinct so I was afraid for him. He would swat at it if he'd really gotten close, and he tried swatting them once I got them into the bowl. My question is, should he be stung by one of these could it make him very sick? I only ask because he is a very small cat, full grown male and only about 4.5 lbs (and he's a little overweight!). I do not mind them here if they are non-aggressive, but I am a graduate student and cannot afford a huge vet bill right now! Obviously you can't know for sure if he is allergic, that'll be up to me to find out, but have you ever heard of an animal becoming sick or dying after being stung by one of these? (other than the spiders, I don't think they could carry off my cat to a nest!)

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  53. I keep finding what appears to be these blue mud dobbers constantly in my kitchen. I have attempted to seal up any holes around light fixtures and such with no luck. I'm wondering if they aren't somehow in my ac ducts, which would mean my attic is infested. Is there a safe way to deter them without bombing my attic? I am highly allergic and even though they are not aggressive I refuse to live with them, those epipen shots are just as painful as stings. So is there a herb or something I can use that will deter them or is my only real option pesticide? I'd really rather not kill them if I don't have to, but I cannot have them inside my house, and over the span of this week I have found sixteen in my kitchen area. I'm hoping they are these, I do have pictures and they look like them so any advice would greatly help.

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    1. Well, you may have to employ a professional pest control service in this case....but make sure they figure out how the wasps are getting in, and remedy that issue so that this is not a recurring nightmare. I would not be surprised if two or three mud dauber species are nesting in your attic if they can get through the vent. I am delighted by your concern for the insects, but there are very few species that are on the endangered list. Blue Mud Dauber is not among them.

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  54. How common are they in Northwest Minnesota?

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    1. I don't know, I've never been to Minnesota....but the species is found in virtually every state as far as I know.

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  55. I just watched a female chase down a spider 3 to 4 times it size..jump on top and then start stingng the hell out of it. then she flew off with it. it was amazing to watch!!

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  56. I have a least 50 of them congregating around the same spot on my house every year...they don't bother me at all ...just very weird they go to the same spot every year

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  57. I have a least 50 of them congregating around the same spot on my house every year...they don't bother me at all ...just very weird they go to the same spot every year

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  58. Would they build a nest in a hole on one of my porch wood rails? I've seen at least 2 with blue wings enter that hole?

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    1. You are observing some other kind of solitary wasp, then. Feel free to take images and use my "Forum" tab above to ask about them.

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    2. I got one black wasp. I am afraid cause I have a 4 years old daughter . I took a picture but that thing flew in the house and Idk where it is. How I can add the pic?

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  59. Would they build a nest in a hole on one of my porch wood rails? I've seen at least 2 with blue wings enter that hole?

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    1. No, they would not. You are observing some other kind of solitary wasp.

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  60. Thanks for the info. I have these wasps every year in my garden. Especially while and after watering. I had already geussed them non aggressive as they've never bothered with me. They are Beautiful accompaniments to my Garden.

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  61. Thanks for the info. I have these wasps every year in my garden. Especially while and after watering. I had already geussed them non aggressive as they've never bothered with me. They are Beautiful accompaniments to my Garden.

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  62. Glad to find out what these guys are! We have a "bachelor party" in the crevice of a post on the porch and weren't sure what type of wasp they were and if we needed to worry about them. I usually have a live and let live philosophy, and these wasps aren't aggressive, so I figured it would be fine if we just left them alone. They're so pretty, plus they eat black widows- they're welcome around here!

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  63. Hello! Just stumbled across this thread after finding a solitary mud cocoon in the UK. The inside area was around 10mm long and 3mm across. Inside was a spider (still alive) with no bug on it I can see. There remains one section closed. Shall I just put them outside? I can't see any evidence of a large nest ... in my bedroom gah!

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  64. If I have a large amount of blue mud dobbers, does that mean I have black widows here. I moved not long ago, I haven't seen many spiders(mostly wolf spiders) and lots of scorpions!

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    1. Not at all. Blue Mud Daubers tend to be opportunists, and they are good at teasing *any* spider out of its retreat. These were common in Portland, Oregon when I lived there, and we had hardly any widows.

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  65. In case you're still wondering, that last image does appear to be C. zimmermanni, specifically the subspecies aztecum. The white hairs are another indication of the species. Great photos - you're just missing C. z. zimmermanni in the post (white hairs, dark wings)

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  66. Thank you very much! Found a lot of their nests in the barn. Now know who they are and happy to host them :))

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  67. Came here looking for this wasp. Sitting in my tree stand currently and have one flying around and checking out the place. I feel much better knowing that they are not aggressive and I will not have to worry about being bothered by one. Huge relief!! Thank you!

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  68. The Chalybion californicum wasps have been visiting my dead & dried gardenia plant located on my covered deck in the Texas Hill Country every evening during the month of May and now into June. From your article, I gather they might be seeking a resting place for the night or could be taking advantage of cooler temperatures during the twilight hours? I’m wanting to understand the behavior of their congregation. My dead plant could still be attracting other small insects or mites that are not easily noticeable or maybe exuding substances. Could these insects be a food source for the wasps, even if the wasps are not visibly hunting? I used an acidifier (organic fertilizer) on my gardenia plant in April, which killed the plant, so might the fertilizer have left residues that are attractive to the wasps? Certain chemicals and/or pheromones can emit odors that insects, including wasps, might find appealing so I am exploring this as a possibility for the evening congregations. I cannot identify the sex differences, but your comment about bachelors resting and gathering may be the reason. Thank you for an informative discussion! I wish I could share my video of their evening sessions!

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    1. I updated this article on June 29, 2022, so it took me a minute to find your comment....I don't think any insects, or chemical residues, on the plant are what is attracting them. I think it is indeed shade during the heat of the day, and a place to congregate at night. That simple. I appreciate your curiosity, and thank you for sharing your observations!

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