larva of Platygaster is at first rather like a small Copepod crustacean,
with prominent spiny tail-processes; after a moult this form changes
into the legless grub characteristic of the Hymenoptera, among which
larvae even approaching the campodeiform type are very exceptional. The
species of Platygaster pass their larval stages within the larvae of
gall-midges.

Wasps, bees and ants, have the ovipositor of the female modified into a
sting, which is often used for the purpose of providing food for the
helpless grubs. Thus the digging wasps (Sphegidae and Pompilidae) hunt
for caterpillars, spiders, and other creatures which they can paralyse
with their stings, and bury them alongside their eggs to furnish a
food-supply for the newly-hatched young. The social wasps and many ants
sting and kill flies and other insects, which they break up so as to
feed their grubs within the nest. It is well known that the labour of
tending the larvae in these insect societies is performed for the most
part not by the mother ('Queen') but by the modified infertile females
or 'workers.' Other ants and the bees feed their grubs (fig. 18), also
sheltered in well-constructed nests, on honey elaborated from nectar
within their own digestive canals. In all cases we see that the
helplessness of the grub is associated with some kind of parental care.

[Illustration: Fig. 19. Larva of Gall-midge (_Contarinia nasturtii_),
ventral view showing anchor process (_a_), and spiracles projecting at
sides. Magnified 30 times. From Carpenter, _Journ. Econ. Biol_, vol.
VI.]

From the Hymenoptera we may pass on to the Diptera or Two-winged Flies,
an order of which the vast number of species and in many cases the
myriads of individuals force themselves on the observer's notice. F.