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A Note on Eumenidae or Potter Wasps in Al Ain

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by Michael P.T. Gillett

(The following article appeared in the Al Ain Newsletter of January 1996.)

The Hymenoptera is one of the largest orders of insects and one that is well represented in the Al Ain region by the ants, bees and wasps. Of the latter, the social wasps (Vespidae) do not have numerous species in Arabia, although at least one, the Oriental Hornet (Vespa orientalis) is common around Al Ain and is, perhaps, one of the most dangerous insects in the UAE. On the other hand, solitary wasps are represented by numerous species in the Al Ain region. This is a rather diverse group, comprising many families of minute to large insects. Notable families, all with large sized species, include the Pompilidae (Spider Hunters), Scoliidae (Chafer Hunters), Sphecidae (Digger Wasps -- many of which hunt grasshoppers and locusts, although some prey on bees and Eumenidae (Potter Wasps -- most of which hunt caterpillars).

Potter wasps are aptly named, as the female insects construct brood chambers in the form of mud pots complete with neck and rim. These are attached to rocks, walls and vegetation. When the pot is finished, the female goes in search of small caterpillars which are lightly stung in the head, but not killed. These are transported back to the brood chamber where they will serve as food for the wasp's offspring. Several caterpillars are placed inside the chamber and above them a single egg is laid attached to a silken thread. More caterpillars (up to about 20) are added and the lid of the pot is sealed with mud. The egg will hatch and the larvae will eat its way through the stock of living caterpillars until it pupates, to emerge eventually as a newly fledged wasp.

For some reason the fig tree in my garden holds great fascination for Potter Wasps although it is not a source of caterpillars. During August and September, and again in the spring, both of the large common species found in Al Ain actively patrol around the tree in mixed bands of up to a dozen insects of both sexes. They occasionally alight on the rough surface of the leaves, but never for long. Caterpillars are seemingly rare in my garden and the Potter Wasps do not appear to build their brood chambers there, either, so that it is all a little bit of a mystery. Why should representatives of two distinct species chose year in and year out to swarm in that particular place? The two species are the pretty yellow, brown and black Delta campaniforme and the much larger, red and black Delta dimidiatipenne, both of which are illustrated in color in Walker and Pittaway's Insects of Eastern Arabia (copies in both the ENHG Library and the Zayed University Library).


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