Wednesday, October 24, 2012

Wasp Wednesday: Four-toothed Mason Wasp

Black-and-white animals are always attention-getters, and that goes for insects, too. Among the more conspicuous of those is the “Four-toothed Mason Wasp,” Monobia quadridens. This member of the family Vespidae, subfamily Eumeninae, is commonly seen at flowers during the summer and fall over most of the eastern U.S.

The common name of Monobia quadridens is somewhat puzzling, and I am not at all certain that it is “official.” It has also been called the “Carpenter Wasp,” and simply “mason wasp.”

This species ranges from southern Ontario and the entire eastern U.S. west to Kansas, New Mexico, and Wisconsin. It is also recorded in northern Mexico. Another species, Monobia texana, exists in Arizona and Texas.

The adult wasps are most often seen on flowers like goldenrod and thoroughwort. Males are easily distinguished from females by the big white spot on their face (females have entirely black faces). When not sipping nectar, the females are looking for nesting sites or hunting for caterpillar prey.

These are solitary insects, and each female selects her own nest location. Much of the time they utilize abandoned tunnels originally bored by the Eastern Carpenter Bee, Xylocopa virginica. Check for such nests along the edge of the roof of your own home. Monobia quadridens has also been observed to evict mason bees (Osmia sp.) from wood borings, killing the bee eggs, larvae, and pupae in the process (Byers, 1972). Abandoned nests of the Black and Yellow Mud Dauber may also be used by M. quadridens. Rarely, the old burrows of ground-nesting bees are used.


Male M. quadridens on sumac flowers

Once she selects a suitable nest cavity, the female wasp goes about hunting for prey. Considering the large size of the wasp, the caterpillars it hunts are rather small: Primarily leafrollers like the Sweetgum Leafroller, Sciota uvinella (family Pyralidae, subfamily Phycitinae); the Dimorphic Macalla Moth, Epipaschia superatalis and Maple Webworm Moth, Pococera asperatella (Pyralidae: Epipaschiinae); the Grape Leaf-folder, Desmia funeralis (Crambidae: Pyraustinae); Schlaeger’s Fruitworm Moth, Antaeotricha schlaegeri (Elachistidae: Stenomatinae); Psilocorsis sp. (Amphisbatidae); Platynota spp. (Tortricidae); and unidentified caterpillars in the family Gelechiidae.

Each caterpillar is stung into paralysis and flown back to the nest. Several caterpillars are stuffed into the bottom of the nest tunnel, and a single egg laid there. The female then collects a mud ball which she fashions into a curtain that seals off that compartment. She will leave a small empty “room” between that cell and the next one along the length of the tunnel, repeating the process for as many cells she can comfortably create. Once filled, the nest tunnel is sealed with a final plug of mud. The empty rooms, called “intercalary cells,” are thought to confuse parasites into thinking that nobody is home.

So, the sequence in a given nest, from the bottom up is brood cell, intercalary cell (empty), brood cell, intercalary cell, and so on, with a final intercalary cell nearest to the nest closure. This last empty cell is called a “vestibular cell.” There are generally less than five brood cells per nest.

Each female wasp may create more than one nest, as long as she is physically able to do so. Inside the nest, each egg takes about two days to hatch. The larva then begins consuming its larder of caterpillars. It takes an average of 4-8 days to finish eating before preparing for pupation.

The wasp larvae do not spin cocoons, but do secrete some kind of “varnish” that they apply over the interior walls of their cells in the course of one to three days. Each larva enters the inactive pre-pupal stage about five days after it finishes feeding. About three days later, the larva pupates (in summer generations; it may overwinter as a pre-pupa later in the year). Ten to twenty-one days elapse before an adult wasp emerges (again, for the summer generation). Males take less time to metamorphose than females. The eclosed (emerged) adult wasp then lingers inside its nest cell for another 2-3 days while its exoskeleton hardens and it is able to chew its way through the mud partition(s) to freedom.

Not all make it, of course. Some orient themselves the wrong way during the pre-pupal stage and are not able to turn around inside their cells once they emerge as adults. Others are victimized by parasites. Mites (Tortonia quadridens and Monbiocarus quadridens), may take a toll, even though they are thought to be scavengers that feed on the remains of the caterpillar prey inside the cells. The larval stage of the bee fly Anthrax aterrimus feeds as an external parasite on the pre-pupal or pupal wasp. Larvae of Amobia erythrura, a “satellite fly” in the family Sarcophagidae, eat the caterpillars stored for the wasp larva, essentially starving it to death. Melittobia chalybii are tiny parasitic wasps in the family Eulophidae that lay their eggs in the larva of the host. This includes Monobia quadridens.

My good friend Joe Cohelo made a nice little video about these wasps. He includes some quality still images at the end. Much remains to be learned about this wasp despite previous studies, and your own observations, videos, and images could help increase our collective knowledge. Personally, I like the idea that these mason wasps can get to leaf-rolling pests even when chemical applications can’t easily penetrate the caterpillars’ refuges. It just goes to show that nature has its checks and balances, and sometimes we should let them operate on their own schedule.

Sources: Buck, Matthias, Stephen A. Marshall, and David K.B. Cheung. 2008. “Identification Atlas of the Vespidae (Hymenoptera, Aculeata) of the northeastern Nearctic region,” Canadian Journal of Arthropod Identification No. 5: 492 pp. (PDF version).
Byers, George W. 1972. “Competitive Supersedure by Monobia quadridens in Nests of Osmia lignaria,” J Kans Entomol Soc 45(2): 235-238.
Krombein, Karl V. 1967. Trap-nesting Wasps and Bees: Life Histories, Nests, and Associates. Washington, DC: Smithsonian Press. 570 pp.
Krombein, Karl V., et al. 1979. Catalog of Hymenoptera in America North of Mexico Vol.2 Apocrita (Aculeata). Washington, DC: Smithsonian Institution Press. Pp. 1199-2209.

118 comments:

  1. Evicted one of these ladies from my bathroom today with the aid of a large glass and a magazine; caught without harm and set free outside again. Glad I did, after reading here.

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    1. Love hearing about wasp rescues! Thank *you* for being kind to insects :-)

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  2. Dear Mr. Bug Eric,
    A friend and I are having a debate about the difference between madon wasps and potter wasps. Can you direct me to any scientific literature that specifies the differences? I cannot find any. Love the blog!

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    1. Philipp: Both mason wasps and potter wasps are in the same subfamily of the family Vespidae. So, the Eumeninae includes both potter wasps and mason wasps. Here in the U.S., only those species in the genus Eumenes are referred to as "potter wasps" because they make free-standing mud nests that resemble tiny urns. Elsewhere in the world there are other genera that create similar nests. Hope that helps; and thank you for the compliment!

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    2. I just looked up what was using my mason bee hive. Its one of these.

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  3. This comment has been removed by a blog administrator.

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  4. Bug Eric, I have one of these in my backyard. I saw it chewing on a hole in some wood constructing the shed. I also saw it walking around a comfrey leaf for some time. However, the one in my yard has a large white spot on the front of its head. Is this the same thing as Monobia quadridens or something different? What does the white spot signify?

    If you'd like me to email a picture, let me know.

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    1. Males of this species have a white clypeus ("upper lip"), so it is possible you observed a male Four-toothed Mason Wasp, yes.

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    2. Good Day Bug Eric...I just stumbled on this blog while looking for identification of a wasp and found it to be a mason. She is a clever Momma building in the small tube of my fountains statuary...not currently in use of course and looks like I won't use it this summer as its occupied now!! I can only wonder how many egg compartments are hidden inside the Cherub. Momma is beautiful!

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    3. Thank you for your amazing degree of tolerance!

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  5. Hi, I just found one of these wasps using my deck as a home. I was wondering if they sting/bite? I have two small children and a husband who is allergic to bee stings. Thanks so much!!

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    1. Assuming these are indeed the wasps you are seeing, then no worries really. Female solitary wasps *can* sting, but you literally have to grab one to get her to do so. Male wasps lack stingers. Social wasps like yellowjackets and paper wasps are another story because they are protecting large numbers of vulnerable eggs, larvae, and pupae in their colonial nests. Thanks for the question; and you're most welcome!

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    2. I think me and my son were just stung by one of these.. It looks right, and we live in the right area where they live. It was getting to be dusk and I was pushing my son in his swing and I see this large black flying insect fly towards him and he suddenly starts screaming and before I can even stop his swing it stings me in the chest. He got stung three times. Twice in one finger on his right hand and once on his thumb on his left. I do not even know if it has a nesting sight nearby, this is the first time I've seen this wasp that I know of.

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    3. This is the same Anonymous as above. Nevermind. My FIL found out what stung us, it was a black wasp and apparently they had built their nest right underneath my son's swing.

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    4. Ok. Solitary wasps in general very rarely sting people, so I am sorry you all had that experience.

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  6. the wasps have set up house in old carpenter bee tunnels.. At first I was happy since the carpenter bees seem to do a great deal of damage. Now my question is should I be concerned? My garden will benefit but my house?

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    1. Bruce, the wasps don't enlarge or extend the existing carpenter bee tunnels to any degree. Any damage was already done by the bees.

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    2. thanks Eric so, I guess these warps are a blessing as are my wildhoney bees

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  7. Thank you so much for the pictures and article!! I have one of these beauty's under my rocking chair in a carpenters bee hole on our front porch. I just witness her carrying a very large larva and trying to stuff it in the hole. She dropped it about 6 times before she finally got it in!! I know this is a stupid question but do they survive the winter? My 4 year old daughter and I have loved watching her this summer:) they are very interesting!!

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    1. Hi, Kelly! I *love* hearing stories like this, so thank *you* for making what I do worthwhile....In answer to your question, the mother wasp you are watching won't survive the winter, but her offspring inside that carpenter bee hole *will* survive, as larvae, snug inside that tunnel. You might want to drill some holes in a block of wood and hang it somewhere (like under the eave of a shed) so that future generations of mason wasps, other wasps, and solitary bees can have a place to nest next summer. You will be surprised by the diversity of species such a "bee box" will attract, especially if you drill holes of varying diameters. Thanks again for sharing your experience :-)

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  8. Hello. Thanks for all of your research. I have finally found out what this beauty is. She has been hanging out by my porch light of a night socializing with my moths. I'm glad to know they don't sting. Do to your efforts she will be spared. Her and her next generations will be welcomed. Thanks

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  9. Hi! I think I just seen one today in Bellingham, wa? Is that even possible? & if not do you know what it could of been?

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    1. Monobia quadridens is an eastern U.S. wasp, Kelsey. There in Washington state it would likely be a Bald-faced Hornet or Blackjacket that you are seeing (those two come to mind immediately, anyway).

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  10. Thank you for identifying this little lady for us. She is building a nursery in the legs of one of our porch chairs. Since she isn't aggressive and is good for the flowers, I think we'll leave her and her babies where they are.

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    1. Thanks for sharing that, Cynthia! Love your attitude :-)

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  11. Thanks for the info.! I have been seeing these every summer for a few years on my back porch by my slider and have been trying to figure out what is going on. They carry the larvae and stuff them into old carpenter bee holes in my cedar siding. The mud plugs always make a bit of a mess on my deck and I've worried about what it was I'm cleaning up. They are very docile and never bother us or our children so I've just let them be. Now I can sleep knowing they are not only NOT doing further damage but are actually beneficial. Plus they are just fascinating to watch. Very helpful information.

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    1. You are most welcome, Dawn. Thank you for the compliments.

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  12. I had one of these ladies trying to make a spot in one of my cinder blocks here in West Michigan from the mud my son was playing. I wanted to leave her alone but I didn't want her close to where my son plays in our back yard. I didn't kill her, I just covered up the plug she was making.

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    1. Solitary wasps like this will not sting unless you grab one, step on one in bare feet, or otherwise contact the wasp directly. They do *not* go looking for *you*, or behave aggressively towards people.

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  13. I have a nest in the ceiling of my porch. I often see the Momma wasp bringing caterpillars into the hole. She already has one hole she filled with mud and uses another hole for entering and exiting. I've also noticed another female wasp sneaking around and the Momma will actually "fight" the other female. It scares my children and I to the point that we don't sit back there often. I'm afraid that they will get stung it that I will because when these wasps do fight that've actually fallen to the ground and on me! I've tried looking up these wasps fighting for nests but have had no luck. Have you ever heard of this happening before?

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    1. Jenny - Thanks for sharing your experience. The "fighting" wasps won't sting innocent bystanders. Competition for nesting spots is keen, but it could also be the wasp versus some parasitic wasp or fly instead. Lastly, a hole plugged with mud is a *finished* nest, not a stopped-up entrance to another nest. Once she completes one nest, mother wasp will start another while she is able.

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  14. Hi Eric,
    My mason bee house has been occupied by 3 very gentle mason wasps. I have trapped about 6 tubes filled with mason wasps for next year's garden. I have 2 questions about the mason wasps.
    1) Do the require any special treatment like overwinter refrigeration and hatching boxes that are used for mason and leafcutter bees?
    2) Are they sociable with leafcutter bees or would they drive them off?
    Thanks

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    1. I doubt that they need any special treatment. Changes in day length appear to be the trigger for emergence from the pupa stage, not temperature changes. I doubt they would "drive off" leafcutter bees, but it might be "first come, first served."

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  15. Being a nice sunny day I decided to sit on my porch,only to find a swarm of thousands of these wasps flying near my roof.I'm scared to death of flying stinging insects.they look pretty similar to the Mason wasp but I'm just not sure.the lone yellow stripe is so thin and the smaller ones have a yellow triangle shape on their face.I live in Louisiana if that helps.should I be worried?stuck in my house at the moment :/

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    1. I think you may have some other kind of wasp, or even a solitary bee species....but no reason at all to panic. Wasps do not go out of their way to hurt people or pets. Meanwhile they are controlling pest insects and pollinating flowers.

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  16. I found your blog after searching to identify the strange flying insect that was making her best in a hole in a spindle on our porch. After identifying her as a female Mason wasp, I researched more and found this while watching her on my porch. I also grabbed my camera and have taken several images of her, but I'm slightly confused over the solitary part. There seems to be a pair of them and the male fits the description as well. He doesn't enter the best, but he patiently waits (stalkishly) on the spindle for her to exit and they will fly off together and return. Any similar observations? I live in AL. Thanks for all the good information!

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    1. Sounds like the male is waiting for a mating opportunity. Male solitary wasps and bees often "hang out" where females are nesting and try and mate with them. Love your curiosity and detailed descriptions. Thank you for sharing!

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  17. Have one of these hanging out on our porch. Really don't want a nest back where the kids are going to play but really don't want to kill it unless of it absolutely has to come to that. Is there a way to know if a nest is going to be built or to prevent a nest from being built.

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    1. Again, this is a *solitary* species, and females don't go out of their way to defend their nest. In fact, they are likely to fly off if approached closely. Unless a kid physically grabs or pins a female, there is not going to be an incident. Please relax. Thank you.

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  18. Hi Eric, glad to see you are still enlightening our ever curious nature of these wasps. I was scraping the house today when I came across a mud pile hooked to the frame of a basement window well. I scraped it into a bucket and after initial research thought it was an old mud dauber nest. Unfortunately my curiosity got the best of me and there were many sealed cavities inside full of curled leaves. I have been searching an hour reading and learning about various wasps and bees and have finally come to understand the wasp that possibly reused an old mud nest was this wasp. I am grateful for your information and hopefully next time I come across a mud nest, I can at least relocate it for the larvas sake.

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    1. Hi there! Thank you for the compliment....It sounds like that particular mud nest was re-used by a leafcutter bee, family Megachilidae. They use cut pieces of leaves to build their nest cells.

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  19. Found out in a very painful way that there was one of these in my laundry room. I did not kill it although it brought me to the ground with its powerful sting. My left inside ankle is still swollen after a day. Did I mention it hurt? IT FREAKING HURT!!!!... read my text. I-T H-U-R-T!!!!!!!!!!!!!!!!

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    1. I'm sorry you had a bad experience with one. Please accept my get-well wishes!

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  20. Hi there, thank you so much for your article. It allowed me to identify a visitor to my garden. "She" was gathering nector from my mountain mint plant. I took pictures, is there a place you would suggest to sharing them?:)

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    1. Glad I could help! As for your images, not sure what to tell you. There are many groups on Facebook devoted to pollinators, wasps, etc; I also post on Flickr periodically, plus i-Naturalist. I don't have a place here on my blog, sad to say.

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  21. Your blog just saved one by me. I was staining my deck and was just on the way to get the spray as it is hanging around and I'm terrified of stinging bugs! Jusr got on google to try to identify it. The comment earlier about them not stinging easily saved it's life!

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    1. Yay! Glad I could be of service to both you *and* the wasp. :-)

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  22. Hi ..I have yellow mason wasps ..using my mason bee holes .. Here is the strange thing .. Each wasp is followed by two hover flies.. What's up with that???

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    1. I suspect they were not hover flies, but bee flies (Bombyliidae, like Xenox sp. that are parasitic in mason wasp nests) or thick-headed flies (Conopidae, which are parasites of adult wasps).

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  23. Im so bummed😔 I just accidently killed one!
    I walked my daughter to her car tonight in my robe and when I went back inside I felt a tickle on my ahoulder so I scratched it,then I felt a stinging and I panicked and instinctively swatted my shoulder and pulled off my robe...when I did,I shook it out and she (I assume since I just read only girls sting) fell out of my robe dead :(
    It looked like a wasp but not??? So I looked it up and it brought me here and now I feel even worse,as I never would have killed it! Uhg...just thought I'd vent here,because you'd understand me feeling bad for killing her 😔

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    1. Aw-w-w, accidents will happen, and our instincts kick in when we are suddenly confronted with something potentially dangerous. Please forgive yourself; and know that I am thankful for people like you who care about other creatures. :-)

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  24. I get many carpenter bees outside my sunporch every spring, followed by many of these wasps later, coinciding with the bees' disappearance. I much prefer the wasps as they're gorgeous and not destructive. Do they kill the bees? Would it be wrong to try to assist them in this? I have a tennis racket and carpenter bees are slow... ;-)

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    1. I do not advocate killing insects that are not a menace to health; but, remember, were it not for the carpenter bees creating the "housing," there would be no wasps following them. ;-)

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  25. Hello. I live in Louisiana and have both Carpenter Bees and Mason Wasps. The bees moved in a few years ago and the wasps about a year or so after. I have been noticing that the bees do not seem to be coming back in the same numbers since the wasps have showed up. Are the wasps killing my bees? Can they live together? Is there something I can do to have healthy groups of both?

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    1. I am pretty certain you still have a balance of both species, just in an area greater than your yard. The wasps certainly don't kill the carpenter bees, and probably rarely displace them. Giant Resin Bees (Megachile sculpturalis) *have* been known to evict carpenter bees from active nests.

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  26. Just saw one for the first time (I think) this weekend. A warm autumn may mean they have a chance to stock another nest in the fall? Certainly a difficult wasp to miss.

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    1. Excellent question, Terry! Most wasps will continue life as normal until the first killing frost. Since many caterpillars overwinter in their larval stage, it stands to reason there should still be prey available to this wasp.

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  27. Enjoying almost-summer afternoon breeze from patio door when I saw a black wasp with white band fly into vent slot of junked CRT TV sitting near patio door awaiting disposal. Before I grabbed my can of encapsulating foam wasp killer -- only used on yellow jackets/hornets trapped inside house -- as frankly I'm petrified of flying stinging insects ever since while down in LA this red wasp stung *the living daylights* out of me & my elbow swelled to size of softball! Now up here in Poconos (PA), I see a unique variety of flying, crawling, arachnoid critters & more which I photograph (praise God for zoom lens) if I can, then Google ID out of curiosity. That's how I found your blog. My heart rate slowed after you stated male Mason wasps don't sting & females aren't aggressive unless cornered (kinda like humans tho we tend to do more than just sting). For now, guess I'll leave old TV *be* (no pun). Appreciate your cool blog, Eric. BTW Happy Father's Day.

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    1. Thank you for sharing your stories and for the compliments. I am a Father to no one or nothing, other than my writings. ;-)

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  28. Witnessed a mason Wasp fight and evict a carpenter bee from our wooden step railing a week ago. The carpenter bee suffered a sting from the wasp and unfortunately it took a couple of days for it to die on our step as the wasp took over her home. Carpenter bees can be annoying but I felt bad for this one.

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  29. I saw one this evening on the top of a bottle I use for an ashtray. I had never seen one before and thought it was a cool, weird looking wasp. I went out about a half-hour later and forgot about it. Well not looking I reached over to take the top off and suddenly the sting made me remember that it was there. Haha wow the tip of my middle finger felt like someone had left a nail in a fire for 30 minutes and then decided to jab it in my finger. Quite a potent sting it has! I will remember what they are now next time I see one. I live in Mechanicsville, Va which is pretty rural where I live and still can not believe that's my first run-in with one. It was a female because it didn't have white on its face. Glad I read that it isn't looking for a fight so I know now to not worry if I see another one. This blog was very informative. Thank you.

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    1. Ouch! I am so sorry you got stung; and I am impressed with your sense of humor and tolerance of stinging things. Thank you for the compliments on the blog!

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  30. Quick question: I have a bee house that I can open the door and look at the tunnels through a plexiglass wall. There are about 12 or so tunnels and I currently have mason bee nests in 2 of them. One day I was looking and there was what looked like a lone ant in the bottom channel. She was there for weeks but never seemed to bother the mason bees. Yesterday I opened the door and found a mason wasp shoving caterpillars in the tunnel. It looked like the body of the ant was still in there (I have a video of it). Do you think it was just bad luck for the ant that the wasp chose that bottom hole? Or is there some other weird explanation you might know of involving ants and wasps?

    Thanks!

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    1. I suspect the "ant" may be the pupa of a bee or wasp, but I'd have to see images at least to understand this. Can we leave it at a mystery?

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    2. I’ve def learned to accept and appreciate nature’s mysteries :) FWIW, I posted a pic on reddit, asking if anyone knew anything about ants and bees in case you wanted to see it: https://www.reddit.com/r/Beekeeping/comments/8hrpc5/ant_squatter_in_mason_bee_house_hes_been_there/?utm_source=share&utm_medium=ios_app&st=JHL6C2Q7&sh=55a802e4

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  31. I keep finding these in my house and I’m completely stumped as to why. I have 4 small children, one of which is extremely allergic, along with myself (my throat will close up within 2mins of a sting). At first we thought they were baldfaced hornets, then thought they were cicada killers, but now seeing more photos of these, I’m convinced this is what we have on our hands. I don’t know how they’re getting in our house, but I’ve been killing them on site. Is there any way I can send you a photo so you can confirm this is the species we’re dealing with?

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  32. Thanks for your informative blog. We've had a pretty big carpenter bee population for years in redwood posts and lattice. But now that population has waned. Mason wasps are definitely on the increase. I agree, they are not aggressive. Today I experienced a "swarm" of about 6. wasps. Could this be the summer "hatch"?

    Thanks

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    1. I have never seen a congregation of this species, so I cannot answer that.

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  33. Your blog is very nice. You may not have an answer for me, but I’m desperately searching for answers. My husband was but AND stung yesterday by a lovely lady who was hiding in his shirt underneath my infant daughter (scary place for her to hide poor thing didn’t make it) he has hemophilia and feels like the sting may have given him a blood thinning side effect. I can’t find anything on the internet about their sting other than cold chills for a couple of days and pain for the first day. Is their sting so venomous that I should seek medical attention for him?

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    1. Unless your husband is experiencing something like shortness of breath, heart palpitations, excessive sweating, nausea, or some other symptom that is out of proportion to a sting, there should be no need for medical intervention. That said, I am not a doctor, so if you have concerns, contact his physician.

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  34. Hi! My girlfriend and I noticed a couple of these lovely creatures carrying worms into the exposed ends of two small pipes on our folding outdoor chairs. One of them has blocked the entrance to it's pipe with mud it looks like; the other is still flying in and out with food. We have been able to capture some great pictures and video of them!
    Is there a way that I could send these pictures and videos to someone interested in the ways of these little ones? I would love to help the research into understanding them more.

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    1. Cool! I do not have the capacity to accept videos, but I always recommend uploading to YouTube, Facebook, Flickr, or another site, then letting us know the URL for it.

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  35. Hi. Thanks for good identification help. We have one of these nesting in our mason bee house. Do I need to worry much about my mason bees? The house is not very full and there are lots of open tubes. Will they coexist okay?

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    1. You are most welcome! Yes, the wasps and bees will coexist peacefully in your mason bee box! :-)

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  36. Do you know if Manobia and related genera are generalists? Are there some species who are specialists? I still have the remains of mud nests in the holes in the bricks of my porch. The house was my Grandma's in the 60s and 70s, then it was my Dad's, now it is mine. The wasps were there for my whole childhood and most of my teens but at some point "went away". Could that have been caused by the removal of trees that once shaded the porch? Maybe the type of caterpillars they preyed on were specific to those trees? Could the increase of car exhaust had an effect? I have a biology degree and a pretty strong background in entomology. I got into entomology (specifically myrmecology) at a very young age. But it was not until much later that it struck me... what the heck happened to those wasps? My Grandma worried that someone would get stung but no one in the family ever knew of this happening. My Dad and I discussed this when he was still alive and we both agreed (very unscientifically of course) that they seem to have "disappeared" around the time my Grandma died. We also used to talk about how Grandma wished they had used solid bricks for the porch and not the ones with holes (the porch was built before my time, I was born in '63). The wasps obviously liked the holes! Anyway, sorry this is meandering and long. I just wonder what happened to the wasps.

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    1. Great question! I think this illustrates one failure in biological research: long term research. The one stunning exception that comes to mind was that project on trapdoor spiders in Australia where one scientist and her students followed a single spider in her burrow for something like 40 years....

      I appreciate very much that YOU are attentive in that way, and I wish I could reward you with an answer that would be more than pure conjecture.

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  37. Fantastic info. These things are often found right where my carpenter bees are found. They look "dangerous" even though I've never noticed aggression like with those jerks the yellow jackets. Glad to know they are beneficial and are not further contributing to the "work" the carpenter bees have already done on my shutters and deck railing : ) I'd love to see a post with photos about how to use other wood pieces to divert them from damaging my human home without totally displacing them.

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  38. Hi .. I noticed those jerk yellow jackets laying in wait in my mason be holes ..presumably to eat them,, has anyone else seen this???i chased them far away!

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    1. What you describe is not yellowjacket behavior. I wonder if it might be wasps in the family Sapygidae, as I have observed behavior like that in *that* family of wasps.

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  39. Thank you so much for this! I found one yesterday in my screen porch and thinking it was a bald face hornet, I killed her. I feel awful now. I make it a point to catch and release all sorts of little critters- I save bumble bees, honey bees, butterflies, spiders, house centipedes etc. My boyfriend gets so annoyed with me for saving everything. They only thing I kill are flies, hornets and mosquitoes ��. I thought this was just another hornet who was going to sting us. If I see more I will release them. I have a question though, I raise monarch caterpillars. I collect the eggs and caterpillars from the wild and rear them in cages and release. Last year I released almost 300. Do these Mason wasps kill monarch caterpillars?

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    1. No, these wasps do not seek out Monarch caterpillars....but while helping Monarch butterflies is all well and good, the focus needs to be on enhancing BIODIVERSITY as a whole. I cannot emphasize that enough. Other insects *should* be preying on your Monarch caterpillars. That is a sign of a healthy ecosystem!

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  40. I have some insects burrowing into the wood shelves on my back porch that appear to be the ones in your article. However, my little guys have 2 dots above the line on their back, which makes them look like smiley faces. I haven't found any pictures online of this variation, except in wasps that are black and yellow. Could you help me identify my wasps? I live in the Tyler, Texas area. Thank you!

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    1. If they are nesting in cavities in the wood, then most likely some other kind of mason wasp.

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  41. Hello, very informative I noticed what i thought was a black hornet in an old carpenter bee hole on my porch, but upon examining it and seeing bring back a grub to hole, I noticed yesterday that the hole is sealed with mud, i started researching and think that i may have a mason wasp nursery. It was really neat watching her i would see her pop her head out hole when i peeked in and she has never been aggressive towards me she is a beautiful insect. And i hope to see the babies. I live in WV.

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  42. Hello Bug Eric! Thanks for this informative blog. I know now that I have one of these in my deck. She is having a hard time getting the grubs and caterpillers in her nest. The deck looks like a grub graveyard! Lol. Everytime she drops one she leaves it and brings back another. Interesting to observe while I tend the planter garden.

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    1. Wow! How interesting. I'm also surprised some kind of bird, like a wren, hasn't noticed and started eating the grubs.

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  43. We have one of these girls nesting on our patio. She's been filling the hollow aluminum tubes in our folding chairs. If we're sitting in the chair she gets up in our face. I'm not sure if she's telling us to move or if she's just checking us out but either way I always end up standing and letting her through. She already built one nest in my roomate's chair. Now it's my turn to stand lol

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    1. LOL! That is a GREAT story! Thank you for sharing your tolerant attitude. <3

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  44. Just found one of these pretty ladies in my house. After properly identifying her with a bug identification app and some quick googling I found your site. I'm allergic to wasp type things, but everything I've read says they are docile. She is hanging out in a cup with paper so I can out her out side. My eves have soooooo many of them flying around though where I used to have carpenter bees... do they fight for space?

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    1. They only take over abandoned carpenter bee nests, as far as I know. Giant Resin Bee (Megachile sculpturalis) is more aggressive, though.

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  45. Hi! Fantastic and very educational thread you've kept up for 6 years. This helped me identify the little wasp trying to make a home in my bamboo trellises on my balcony garden in Toronto. She totally ignored me and let me get really close to take pictures (so I could better identify her). I'm happy to let her build nests in them - plus, now I have somebody to help me pollinate my garden, since there aren't any bees up here to do it for me. I've always been gentle with and resistant to hurting bugs thanks to my dad, but I'm even happier to be able to coexist with them in a mutually beneficial way. Thanks for this!

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  46. Hi Bug Eric,
    Hi, my name is Hannah and I am 7 years old. I love watching and studying insects. My mom and I found a mason wasp making a nest in a piece of dead bamboo. I found the piece of bamboo in the woods and then the next thing I know there was a wasp making a nest in it! The piece of bamboo is right next to our porch and we know the eggs will hatch soon. Can we move the piece of bamboo? Also, how long does it take for the wasp to become an adult after hatching? Thanks.

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    1. Hi, Hannah! When the wasps emerge will depend on what species they are, but my bet is that they won't come out until next summer. Yes, you can move the bamboo now that the nest is finished (you can tell by the mud plug).

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  47. Hi. I'm in central CT and have not seen these around before. This summer we suddenly have quite a group on and around our deck. Very docile, but I'm wondering about the "solitary" aspect, they only interact with each other as I've seen borers do, i.e. chase each other away from whatever seems worth protecting at the moment. White face threw me at first, I'm highly allergic to bald face and they are not welcome around my home. I suppose the question is do they normally congregate in goups of up to 10 or so within a 100-200 sq. ft. area? Can't follow anyone back to a single nest, they just seem to like the warmth, and I do have gardens surrounding the deck. ~ Thank you for what you do! ~ Mike

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    1. Probably males looking for opportunities to mate with the more scarce females. That would account for the numbers. Thank you for the compliment!

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  48. Hello Bug Eric! We live in southern Ontario. For the last 10 days or so we have noticed black wasps in our backyard, particularly flying under our deck. We had a pest control company come to see if they could locate a nest. The technician crawled under our deck and said he couldn’t see a nest. He only saw a few wasps flying around the backyard but wasn’t sure where they were coming from. I’m not sure if we have four-toothed mason wasps or bald faced hornets. I have researched both species and from the photos I have seen on your blog and on other sites, they look like the four-toothed mason wasps. The only reason I’m not sure if that is what they are is that I read they are solitary. Well, we have many of them! There have been moments when we have seen 5 or 6 fly in or out at the same time or have 3 or 4 flying around the backyard at once. Is it possible that we have several living under our deck in separate nests or would they possibly be living in one large nest together? We have children and are anxious about being stung. I read that the four-toothed mason wasps are not very aggressive. Will they become aggressive if you get too close to their nest? Since we don’t know where the nest is, we’re not sure if we’re getting too close!
    Sometimes they fly toward us and we back off or run away. Thank you for your help!

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    1. Males are probably hovering in the vicinity, looking for opportunities to mate with the females. That would explain the numbers. You might spook the females if you get too close to their nest, but your risk of being stung is virtually zero. Oh, the males are likely the aggressive ones, and they have no stingers.

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  49. Hey! I just seen on of these, looked like a female on my front deck searching all over different wooden surfaces. She didn't seem aggressive at all thank goodness cause I was horrified at first. Looked it up and found this page because I have never seen a wasp like this one yet before. I live in Kentucky.

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  50. Do you know if there is another wasp that would decapitate the Mason Wasp? There is one on our patio where this clearly happened... pretty clean hit, kinda sad. I have a pic of it because of my curiosity, and I haven't found anything online yet. I've only seen certain wasps decapitating bees.

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    1. I have no idea what happened there. Any number of predators, or even scavengers could have done that. Ants will do that to dead wasps and other insects....

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  51. Maybe my last inquiry was too detailed, or technology failed and you never received it. Is this better: Are there any other insects that attack the four-toothed mason wasp?

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    1. I don't get enough comments to moderate daily, so I do it about once per week....Wasps of all kinds have many predators, so I cannot answer this easily. Also, they die naturally and are then scavenged by other animals.

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    2. Ok! It was just such a strange thing, keep up the great work! Thank you for the response!

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  52. I live in Maryland and keep seeing a single black and white wasp that comes up to me while I’m sitting in the wood steps outside. The wasp obviously wants me to move so I move away and it disappears under the steps. I didn’t see a nest at first but noticed it’s going into a hole in the wood step. It stays there for a second then comes out and flys away. Is this a mason wasp? Is there a nest in that hole? Thanks for your info!

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    1. Sounds like a mason wasp female with a nest in the step, yes. She'll be finished and departing within a week, maybe two, maybe already. I was on vacation so pardon the delay in replying.

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  53. I have a wooden swing with carpenter bee holes/tunnels. Yesterday, I noticed that the holes are filled with mud. Today I realized the mud is from 4-toothed mud wasps (thanks to your post). BUT, there is a nest under the swing. I must have swung there for an hour and, not realizing they were there at the time, they didn't sting me. My question: I want to use the swing... How do I get the nest out without harming myself or them? I really want to use wasp spray at dusk. I am allergic to wasps

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    1. Shoot, I only approve comments about once per week. Hope you haven't done anything because you don't need to. If you have been using the swing all this time and have not had any issue, then you won't have any in the future. The female wasps are solitary and so busy with nesting they have no interest in you. Your chances of getting stung are pretty much zero. Social wasps like paper wasps and yellowjackets are a different story.

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  54. I have one of these that has killed off my 5 plus years Carpenter bee family that called my back porch home. I'm confused about this creature. In the beginning of your explanation you say
    "The common name of Monobia quadridens is somewhat puzzling, and I am not at all certain that it is “official.” It has also been called the “Carpenter Wasp,” and simply “mason wasp.”
    Then a paragraph or two down say: Monobia quadridens has also been observed to evict mason wasps from wood borings, killing the bee eggs, larvae, and pupae in the process (Byers, 1972).
    So are they mason wasps, and if so the second above mentioned exert taken from your explanation from above is contradicting itself.Could you please explain what I may be misreading ? I want my carpenter bees back��

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    1. Corrected, thank you for bringing the error to my attention. The wasps have been known to evict mason BEES from their nests. Presumably carpenter bees are too powerful to forcibly evict.

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  55. I live in NE Texas and when I went out to feed my goats yesterday I saw dozens of these wasps flying all over the place. I had to catch one to get a close look and sure enough...I am certain it is the mason wasp. Like I said...there are dozens of them, both male and female all over the place. I do have a lot of carpenter bees every year but have never seen these in force liķe this. Is it because there are plenty of holes for nests? Something seems to be attracting them. I am glad to see them but if this is uncommon behavior is it possible they are something else? They certainly look like mason wasps in every detail. If so then BYE BYE garden caterpillar.

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    1. I would need to see actual specimens to make an accurate identification. In any event, they are unlikely to make a negative impact on your garden, but simply keep the ecosystem balanced.

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  56. I just got stung by one while I was asleep. I Google searched it with a photo and was lead to this article. Great information about them. I'd never heard of them before. Unfortunately, this lady wasp didn't survive, as I woke up and slapped my leg in the dark when the pain hit. Not sure how she got in my bed? I just hope it's sting isn't as long lasting as a red wasp.

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    1. Ouch! I am so sorry you had this unusual and unfortunate experience! I am having to go through old comments to reply because Blogger and my browser have made comments almost impossible. My apologies.

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  57. One of these has made a nest in the leg of a porch chair i sit in all day. I am trying to be tolerant even though she flys very close to me. I am the "bug rescuer" at my job and do not wish to disturb her or her brood. Thanks for reassuring me that she is docile!

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  58. I took a photo several years ago of a female with two males riding on her back as she visited flowers. I found your article while trying to find more information on this behavior, or just mating behavior in general. No one seems to know about the mating behavior in detail, just what happens after she mates and is prepping the nest. I haven't figured out how to attach that photo, but as soon as I do, I will send the photo as well.

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  59. Hi. Where do mason wasps go at night once they’ve sealed their nest?

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    1. That is an excellent question! I do not know the answer to that. I know that male mason wasps usually "sleep" singly, by curling their bodies around a stem or twig. I don't know what the females do.

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