Page 112 - BBC Wildlife Volume 36 #10

OURWILD WORLD
INVERTEBRATES
What is the diference between
a grub, a caterpillar and a nymph?
These are names for the immature nymphs. If in doubt, it’s usually safe
Aforms of insects whose life history
involves a metamorphosis. In some,
such as house fly maggots, beetle
grubs, crane-fly leatherjackets and
moth and butterfly caterpillars, the
transformation happens all in one go,
during an intermediate pupal stage. In
the case of dragonflies, mayflies and
grasshoppers, however, metamorphosis
is gradual, each youngster passing
through several developmental stages
(instars) separated by a moult. These
forms are known collectively as
The Explainer
Evolutionarily
stable strategy
Male walrus:
unlucky in love
(mostly)
The concept of evolutionarily
stable strategies emerged from
the mathematical discipline
known as game theory. A strategy
is evolutionarily stable if it cannot
be bettered – as long as most
of the population adopts it. This
helps explain, for example, the
evolution of cooperation; how
animals make decisions about
when they should fight or flee;
and why most species produce
equal numbers of males and
females, even though a minority
of males in many species (such as
walrus) father the majority
of ofspring. SB
112 BBC Wildlife
to use the broadest term, larva – a bit
of a catchall that can also be used
for the young forms of other
animals that undergo some form
of developmental metamorphosis,
including amphibian tadpoles,
lamprey ammocoetes, crab
zoea, sea urchin plutei,
the planulae of jellyfish,
corals and anemones,
and literally dozens A caterpillar feasts on
milk parsley before
of crustacean forms.
pupating, to emerge
Amy-Jane Beer as a spectacular
swallowtail butterfly.
DISEASE
Do wild animals get cancer?
Wild animals do indeed get cancer – causing their numbers to plummet by
Athough because cancer tends to be a up to 80 per cent. Sea turtles suffer from a
disease of older age, and because life in the cancer called fibropapilloma, which forms
wild is often brutal and short, few animals obvious tumours on the flippers and around
will manage to live long enough for cancer the mouth and eyes. The incidence of
to take hold. fibropapilloma has increased ten-fold over
There are, though, some notable the past decade, and there are suspicions
exceptions. An infectious and lethal cancer that pollution is to blame.
known as devil facial tumour disease, which But it’s only a suspicion. In fact, the roles
is spread by biting and was first identified of environmental problems in the incidence
in 1996, has devastated Tasmanian devil of cancers among wildlife have barely been
populations over the past two decades, studied at all scientifically. SB
Tasmanian devil
facial tumour disease
is a transmissible
cancer alicting this
marsupial carnivore.
Caterp
tasmanian devil: Dave Watts/naturepl.com; treehopper: Lucas Bustamante/naturepl.com ar: Terry Wh ttaker/2020VISION/NPL; wa rus: Theo A
ofs/M nden/FLPA;
October 2018