42 | New Scientist | 21 March 2020
benefits nature provides for us. Honeybees
may be the prime pollinators of many
cultivated fruit crops, but wasps and other
insects pollinate most wild flowers. Indeed,
some plants rely exclusively on wasps. Among
them are almost 100 species of orchids,
including helleborines. These widespread
but scarce plants of woodland edges have
a cunning trick to entice pollinators. Their
flowers produce the sort of volatile chemicals
that other plants emit when under attack
from caterpillars, which lure predatory
wasps hoping to find prey. The wasps then
sip the nectar in the orchid flowers, which
contains soporific agents – possibly alcohol
from fungal contaminants – that slow them
down, increasing the likelihood they will pick
up pollen. Without their tipsy wasp pollinators,
these elegant plants would become extinct.Pest control
Wasps also benefit us even more directly.
They are the third most important predators
of insects after birds and spiders. They use their
powerful triangular jaws to kill prey, snatched
from plants or from mid-air. Once the victim’s
nutrient-poor wings are scissored off, the
dismembered bodies are taken away to feed to
the ravenous brood back in the nest. A mature
wasp colony is reckoned to take between
3000 and 4000 prey a day at the height of the
season. By one estimate, in the UK alone, wasps
eat 14,000 tonnes of insects each summer.
They target woodlice, spiders, flying
beetles and, less endearingly, butterflies and
honeybees. But they also make quick work
of many serious crop pests, including aphids,
caterpillars, plant bugs and flies. There have
long been anecdotal reports of plagues of
flies on private estates after overzealous wasp
nest clearances. In the early 20th century,
small, umbrella-shaped nests of paper wasps
were placed around Caribbean cotton fields
to control infestations of voracious moth
caterpillars called cotton bollworms. Likewise,
in the sugar cane fields of the Philippines,
paper wasps were used to help suppress sap-
sucking planthoppers. Recent research reveals
that another paper wasp, the provocatively
named Polistes satan, can control the larvae
of two of the world’s most rapacious pests,
the sugar cane borer and the fall armyworm,
which eats crops including maize.
Even the sting in a wasp’s tail has potential
to help us. Wasp venom evolved to kill prey,
but social species also use it for defence. Their
succulent, protein-rich grubs are a favourite
of the misnamed honey badger and honeyWhat is a wasp?
Say “wasp” and most people
think of social wasps of the family
Vespidae, often called yellow
jackets in North America. These
relatively large, mostly black-and-
yellow species live in colonies of
between 50 and 10,000
individuals and inhabit nests of
paper-like material made from
chewed wood pulp. Yet they
comprise less than 4 per cent of
more than 110,000 known wasp
species.
And less than a third of wasp
species have evolved what we
tend to think of as the defining
wasp characteristic: that
painful sting. Stinging species are
predatory, whereas the remainder
are parasitic. And the vast
majority of wasp species are
solitary, often living secretive lives
that are easily overlooked.
Wasps come in myriad
varieties. Pale, flimsy fairy wasps
parasitise insect eggs. As little as
0.14 millimetres long, they are
possibly the smallest insects.
Ant-like gall wasps have
chemicals in their stings that
induce bizarre growths called
galls on plants. Their offspring
then develop within these
structures, which include ball-like
oak apples on oak trees and
moss-like robin’s pin-cushions on
some shrubs. Spider-hunting
wasps stock a burrow with
paralysed but living arachnids on
which their larvae then feed.
Potter wasps make nests of mud.
Mason wasps burrow into loose
mortar. And ichneumon wasps lay
their eggs inside moth
caterpillars.
Whatever form they take,
wasps – along with bees, ants and
a whole host of other svelte,
narrow-waisted insects – belong
to the order Hymenoptera, from
the Greek meaning membrane-winged. These insects have four
wings, a larger front pair and
a smaller back pair latched
together by a row of microscopic
hooks (the hamulus) to make
a more efficient single aerofoil.
However, they don’t adhere to the
conventional three-part insect
body plan of head, thorax and
abdomen. Instead, the
first segment of the abdomen
is fused to the thorax to create
a compound body called the
mesosoma. Then there is a
narrow, stalk-like waist between
the mesosoma and the rest of the
abdomen. This acts like a
universal hinge, allowing the
posterior section to be pointed
in almost any direction, which
is particularly useful for species
with a sting in the tail.
Vespidae wasps shared a
common ancestor with bees some
175 million to 200 million years
ago. The main difference betweenthem is that bees feed exclusively
on nectar and pollen, whereas
wasps have more wide-ranging
tastes. Adults may visit flowers to
take the odd sip of nectar for
energy, but small insects are the
main source of food for wasps
and their larvae, and they aren’t
above dining on carrion and ripe
animal scats. With bee species
numbering a mere 25,000, you
might even say that they are just
specialised, vegan wasps.“ With a quarter the
number of species,
you might say
that bees are
just specialised,
vegan wasps”