The ordinary wasps are acquaintances of every one, but the solitary or
keyhole wasps are not so well known, although they are far from uncommon.
They are little narrow black insects striped across the body with yellow,
belonging to the genus _Odynerus_ (pl. A, 9), and might hardly be
recognized as belonging to the same family as the true or social wasps.
Still they have considerable powers of stinging, and fold their wings
lengthwise when at rest like their larger relatives. I dare say some people
may have noticed that a wasp's wing sometimes assumes a narrow straight
form, quite unlike what it is when expanded. This is due to the wasp being
able to fold its wing lengthwise like a fan. The wasp tribe are, so far as
I know, the only stinging Hymenoptera which have this power.
[Illustration: FIG. 5.]
They make their nests of mud, etc., in crevices of walls, in banks, in
plant stems, and often {25} in most inconvenient places, such as keyholes,
etc. Some of the solitary wasps have a very curious habit of making a
tubular entrance to their hole. These may sometimes be seen projecting from
sandy banks. The tube is composed of a series of little pellets of mud,
which the wasp by degrees, with the help of its mouth secretions, sticks
together till a sort of openwork curved tube of sometimes an inch long is
formed (fig. 5). This curve is directed downwards, so that the wasp has to
creep up it before reaching the actual orifice of the nest. It looks as if
the first shower of rain would wash the whole structure away, and I have
very little doubt that it often does so. The object of these tubes is
difficult to appreciate. There is a bee on the continent which makes
straight chimneys above its holes, so as to raise the entrance above the
surrounding herbage; possibly these solitary wasps once required {26} their
tubes also for some such purpose, and have continued on truly conservative
lines to build them long after all usefulness has passed away from the
habit; anyhow they are very interesting and beautiful structures. I have
found the tubes of one of our rarer species projecting perpendicularly out
of the level sand, but even then the tubes were curved over at the end, so
that the wasp had to go up and down again before entering its actual hole.
The Rev. F. D. Morice in 1906 found the tubes of the same species in
numbers projecting from the walls of an old stuccoed cottage situated close
to the locality where I found mine, so it is evident that more than one
situation suits its requirements. The solitary wasps provision their cells
with caterpillars, stinging them in the same way as the fossors do. One
very peculiar genus, of one species only in this country, has its body much
narrowed at the waist by reason of the constricted form of the basal
segment; it makes a little round nest of clay which it suspends from a twig
of heather or other plant. This species is rarely met with except on the
heathery commons of Surrey, Hants, Dorset, etc. The {27} solitary wasps are
subject to the attacks of cuckoos belonging to the jewel fly or _Chrysis_
tribe; these behave differently from those belonging to the aculeate
groups, as their larvae do not eat the food laid up for the wasp, but wait
till the wasp larva has finished feeding up, and then devour it. Unlike as
these cuckoos are to their hosts in their brilliant metallic coloration,
etc., they have structural characters curiously like theirs, so that even
here a common parentage in bygone generations may be reasonably suspected.
At present, however, they are placed, except by a few systematists, in
quite distinct families of the Hymenoptera.
In general form these solitary wasps resemble the fossors more than the
bees; they have mostly short tongues (I think all our British ones have),
and their hairs are simple or more or less spirally twisted.
* * * * *
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