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).