Page 116 - World of Animals - Deadly Predators

PREDATORY
BEETLES
The most species-rich group in the animal kingdom, beetles
have adapted deadly and unusual methods of attack
Words Rachael Funnell
eetles are from the order of insects known
as coleoptera, a group that contains around
400,000 species. They are widespread
across the globe, inhabiting almost all
Benvironments except the ocean and polar
regions. Such a vast range of species and habitats
has produced an array of adaptations, from defence
mechanisms to hunting techniques.
One of the most unusual examples of predatory
beetles is the bombardier beetle. Named after the
section of the US Air Force responsible for aiming
and releasing bombs, it should come as no surprise
that bombardier beetles are well armed when it
comes to hunting. There are over 500 species, all
of which share an ability to project searing hot acid
from their abdomens when hunting or under attack.
The incredible biological weapon is the result of
hydroquinone and hydrogen peroxide mixing together,
creating a foul-smelling substance, which generates
an immense temperature change, heating the fluid to
almost 100 degrees Celsius. This change creates gas,
increasing the pressure in the beetle’s abdomen and
forcing the fluid out at great speed. Most bombardier
beetles direct their bodies towards their intended
victim but others are able to rotate the gland to spray
in a range of directions.
Much like its namesake, tiger beetles can run at
immense speeds thanks to their unusually long legs.
There are 2,600 species of this beetle, which includes
the fastest insect species in the world; Cicindela
hudsoni, found in the Australian deserts can run at
eight kilometres (five miles) per hour. This might not
sound fast but it’s the equivalent of the beetle running
120 times the length of its body per second! This speed
comes at a price however, as when in pursuit of prey
they can run so fast that they’re unable to process
vision and are essentially blind. The beetle has to stop
and give its senses time to catch up before continuing
the chase. When this happens, the prey can escape by
freezing and confusing the beetle. Tiger beetles are
able to run at such immense speeds without tripping
thanks to their antennae. The two sensory appendages
hang ahead of the beetle’s head, gliding over obstacles
but giving the beetle time to react.
If the tiger beetle gets within biting distance of its
prey, it pierces its victim with sword-like mandibles,
then sucks out the soft internal tissues. The size of
the mandible varies according to the species and
dictates what insects they’re able to hunt, with smaller
114 114
mandibles adapted for smaller insects. This means
several species of tiger beetle often share a habitat as
they don’t compete for the same prey.
Not all predatory beetles are so active in their
attack, as demonstrated by the ant nest beetle. These
manipulative killers begin their predatory behaviour
from as early as the larval stage, when they make their
way into the nests of worker ants. Here they disguise
themselves by secreting substances to attract the
ants, giving them safe passage through the nest. As
they grow they progress from feeding on the ant eggs
to eventually using their mature pincers to pierce the
bodies of the grown ants, drinking their liquid insides.
It’s also believed they are able to use an acoustic
mechanism to mimic the sound of a queen ant, again
allowing them to move within the ant’s nest without
attracting any hostile attention.
Liquifying prey is common among beetles, occurring
in many ways. The Devil’s coach horse beetle, Ocypus
olens, hunts worms, molluscs and moths, and is even
capable of digesting carrion. The beetle first kills its
prey using its immense mandibles, pulling the prey
apart and mixing the tissue with a digestive secretion
from its mouth. The process eventually forms what’s
known as a bolus, a ball of semi-digested food, which
is repeatedly chewed and secreted until it becomes a
liquid and is ingested.
When threatened, Ocypus olens will raise its
abdomen and open its jaws in a similar defensive
technique to a scorpion. This action of raising the
abdomen has also given it the common name cock-tail
beetle, and while it’s incapable of stinging it can give a
painful bite with its strong mandibles.
The tiger beetle is
the fastest known
insect in the world
© Thinkstock