Thursday, January 7, 2010

Mud Masterpieces

Solitary wasps are among the most amazing architects in the animal world, many of them creating beautiful nests in clay and sand. Each such dwelling will house a single offspring, provided with food in the form of paralyzed spiders, or insects of one sort or another. Sometimes more than one cell is created and the resulting multi-unit residence can be quite astonishing, too.

Perhaps my own personal favorites are the “potter wasps” in the family Vespidae, genus Eumenes. Females craft exquisite urns about the size of a marble, but usually complete with fluted “neck.”

She finishes one of these containers in its entirety before going off to hunt small caterpillars. She paralyzes several and stocks the pot with them. She then lays a single egg inside the clay sphere and seals the top with a final plug of mud. Inside, a larva hatches from the egg to find fresh food (paralyzed victims do not spoil like dead ones would). Once it has fed and matured, the larva molts into the pupa stage, and an adult wasp hatches a few weeks later, if the pupa is not overwintering for a longer period. The new adult chews a large exit hole in the side of the pot, crawls out, and flies off.

More commonly seen than potter wasp pots are they clod-like structures build by the black and yellow mud dauber, Sceliphron caementarium, in the family of thread-waisted wasps (Sphecidae).

The nests of this wasp are usually a cluster of several cells all covered in additional layers of mud. Some nests can be quite weighty, and thus are usually adhered beneath rock overhangs, or plastered under bridges and other man-made structures. Only one female is responsible for each nest, stuffing each cell with paralyzed spiders as food for the larva in each cell.

Another spider hunter is the aptly-named “pipe organ mud dauber,” Trypoxylon politum, family Crabronidae, found throughout most of eastern North America. Each female normally fashions two or more adjacent mud tubes, again adhered to a flat surface.

Each tube is actually a series of cells arranged in a linear fashion, partitioned on the inside. Trypoxylon are also spider-hunters, but in T. politum, they often work in pairs, male and female. While the female hunts or gathers mud, the male stays at home to defend the nest from potential parasites, predators, and rival wasps looking to usurp the rightful owners. The male has a wicked-looking hook on the underside of his abdomen that may help anchor him to the nest or substrate while doing battle. New nests of T. politum will be intact, while old nests will have large round exit holes down the length of each tube.

There is one other group of spider-hunting wasps that are accomplished masons. Spider wasps in the family Pompilidae, tribe Auplopini, construct delicate mud barrels to hold their spider prey and larval offspring.

Those in the genus Auplopus are small, with a widespread distribution. Phanagenia bombycina is a slightly larger wasp found east of the Rocky Mountains. Ironically, these wasps often build their mud cells inside the old nests of the pipe organ mud dauber.

Many people destroy the mud nests of wasps when they find them attached to their own home. They think the nests are an eyesore at best. Please consider tolerating them instead. Once finished constructing their nest, the female wasp goes off to build another somewhere else. She won’t “attack” even while building her nest. Solitary wasps are not at all aggressive like social wasps.

Those of you more scientifically inclined might consider “rearing” mud nests that you find. While you usually know what species will come out of one, there are many species of parasites that could emerge instead. Host-parasite relationships are not terribly well known, and you could make a significant contribution to science.

13 comments:

  1. Great post, Eric. I've always thought it was so cool that a potter wasp's nest happens to look like a human urn.

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  2. Very interesting post, thanks! We have lots of the pipe organ builder here. I have seen the one that builds the mud barrels once. I've never seen the first one listed, the potter. I'm going to have to start looking harder! Very neat. Thanks again.

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  3. How fascinating. I'll never destroy a mud nest again! Where are the potter wasps? I've never seen anything like that before! ~karen

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  4. Very cool and informative post. Here in Michigan we had blue thread-waist wasps (Great black wasp?) living in an abandoned doghouse. They never bothered us at all, and looked so beautiful resting on our zinnia flowers. We will watch to see what happens this coming spring. With so much hysteria about wasps, it's nice to see a post about less aggressive ones.

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  5. Thank you all for the nice compliments. KaHolly: Look for potter wasp nests in sheltered situations, like around recessed window frames, in tree hollows maybe...Though potter wasp nests can also be quite exposed. I've seen them glued to the needles of an ornamental pine here in Tucson. Oldpoetsoul: the blue wasps are probably the "blue mud dauber," Chalybion californicum, which is found coast to coast. They "remodel" old Sceliphron nests. Chalybion nests are very "lumpy" compared to the original maker's nests.

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  6. Very interesting post Eric. Even though I live in an area that all these wasps should be found, the only ones I've noticed as of yet are the black and yellow mud dauber. We have many of their tell-tale nests around on farm, usually hanging inside one or more of the sheds. I've collected a few of the nests late in the fall simply because they are so unusual and make great props for insect programs. I will be on the look out for the little potter wasp "urns". I guess I wasn't thinking in terms of something so small. Now that I know what to look for with any luck I will find one.

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  7. It's interesting to think of the natural selection processes that drove the evolution of all those different nest designs. Why would one species have found it beneficial to build urn-shaped nests, while another builds tubes?

    I very rarely find mud-wasp nests, but it would be neat to try placing some screening around them to contain the adults when they emerge, something I'd never thought of.

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  8. A great read with fine photographs. I'd love to find some potter wasp vases!

    Perhaps I'll see you in the field - maybe along with our mutual friend Steve G.

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  9. Thanks for writing about this. You've just explained the mysterious structure in the garage.

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  10. Fantastic post, thanks for being there to "answer" th question of the fluted wasp nest. I'll be grabbing the field guide right away

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  11. Thanks for posting this so I could identify who created my little pot. I wonder if this wasp's structure was the inspiration for native americans and other cultures clay vessels shape.

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  12. I came across this post when trying to identify what I think is a potter wasp next (but am not certain, because it looks smoother than the picture shown here). Anyway, although I suppose that the chance that the last commenter will come back and see this reply is small, I did find a reference that the potter wasp nests did in fact serve as the inspiration for native Americans' clay vessels shapes: Animal Architecture (Originally published as Tiere Als Baumeister.) New York, Helen and Kurt Wolff. (ISBN 0-15-107251-5) (1974 1st edition). (Actually I read a description that that's what it says, but I didn't look up the book but hopefully the reference is right.)

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  13. Thank you, Larry! I suspect that the "quality" of pots varies with the type of soil available to the wasp. Here in Tucson, the soil is dusty, sandy, doesn't hold together very well. So, the nests are sometimes a little "rough around the edges."

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