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 wasps 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.

62 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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  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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