Potter wasps

Potter wasps are solitary wasps, although they share similarities in structure with the social wasps. In fact, they are generally considered to be in the same family, Vespidae, and belong to a distinct, separate subfamily, Eumeninae.

Many potter wasps, such as the one above, can easily be recognised by their distinctive shape. They are generally long and thin, even more so than the Polistine (paper wasps). Many also have a generally long petiole (“waist”), linking the thorax and abomen. This applies especially to members of genera such as Eumenes, Delta, Phimenes and several others. However, some species of lesser-known genera such as Abispa, Rhynchium, Allorhynchium, Odynerus and others display a less typical body shape more typical of Vespid wasps. Another thing to note about potter wasps is that when at rest, their wings are usually held at an angle, similar to the Vespid wasps, instead of folded over their backs at a very narrow or overlapping angle like other solitary wasps such as the Sphecids or Pompillids. The species shown above is Delta pyriforme, a common species in East Asia and most of South China. The species shown below is Rhynchium quinquecinctum from Hong Kong (found in much of South China), one of the more stout-bodied species.

Potter wasps make their nests of mud, and in many cases the individual nest cells resemble old style earthen pots, thus their name. Generally the nest is constructed in a shaded area. Some small species build a row of "pots" along a tree branch, but most of the larger species build just two or three in the same area. There are other species which build their nests in crevices or gaps in bamboo stems. I have not found the nests of these. The wasp generally visits a rather wet or moist patch of sandy soil or mud, moulds some mud into a ball and flies back to her chosen nest site, and moulds the mud into place before flying off to collect more. The mud generally dries very quickly, so layer after layer is quickly set in place. However, the wasp usually makes a great many mud-collecting trips just to get the nest set up. Once the nest is complete, she starts hunting for prey.

The Rhynchium haemorrhoidale in the photo below is in the process of adding new layers to the existing nest. Like the mud daubers, many potter wasps build the new nest just next to the old ones. Photo copyright and courtesy of Tan Siong-Kiat (Singapore).

The main prey for many species of potter wasps are various types of caterpillars, and they often use pest species. The caterpillar is generally gripped in the mandibles of the wasp, pinned down and stung, which paralyses it without killing it. The wasp flies and walks all the way back to the nest, dragging the caterpillar along in her mandibles.

As a side note, many potter wasps have distinctively-shaped heads, best viewed from the front. The mandibles are often long and thin and very sharp, almost comical-looking, almost tweezer-like. I used to wonder why they had such mandibles, until I watched a potter wasp in the process of catching a caterpillar. The sharp mandibles efficiently gripped into the soft body of the caterpillar like a pair of forceps, ideal for this type of prey.

The paralysed caterpillar is placed into the nest. Some species put several small caterpillars into a single nest, while others use just one larger one. An egg is then laid in the nest. The wasp then seals up the nest with another layer of mud after this stage. The caterpillar is thus consumed alive following the larva’s hatching. The larva then pupates, and the emerging adult wasp breaks through the mud nest to begin its adult life.

Potter wasps are totally harmless to humans, and should never be killed; they are important for pest control in gardens and farms! A potter wasp can sting, but ONLY if she is squeezed or handled roughly with bare hands! A potter wasp will not attack on her own accord, not even if disturbed in the process of building her nest; indeed, many such disturbed individuals simply abandon the nest site! Potter wasps are also interesting and magnificent creatures, and provide great observation to interested people. Personally I feel that even if one is allergic to wasp stings, there is no need to remove them from the area, as would be necessary with social wasps. To avoid being stung by them, simply do not touch them.

However, potter wasps sometimes choose to construct their nests on windowsills, ledges or corners and walls of houses. To me, these nests are works of art, but many people find them unsightly. The wasps can be discouraged from building nests on these locations by manually chasing them off repeatedly with a long-handled brush; they will soon leave. Nests can be destroyed and the remaining stains scraped off or painted over, or removed by vigorous rubbing with a wet cloth.

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