Amazing Assassins

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Published on: Jun. 2, 2003

Last revision: Nov. 15, 2010

Missouri sportsmen could learn a lesson in patience and stealth from assassin bugs. Some wait for victims in daylight, while others hunt a midnight snack. Some may even be stalking YOU! Most prey on other insects, but two of Missouri's nearly 40 species feed on blood.

You can rightly call assassins "true bugs," members of the order Hemiptera. True bugs resemble beetles or roaches at first glance, but a closer look reveals important differences. The front pair of wings is leathery at the base, but membraneous in the outer half. At rest, they cross over the insect's back in an X pattern. These bugs have piercing-sucking mouth parts, too.

Assassin bugs are further segregated into the family Reduviidae (Reh-deu VIE-i-day), with roughly 5,000 species worldwide. Their distinguishing feature is a groove on the insect's "chest," into which the short, stout beak folds when not in use. Tiny ridges run across this channel, and the bug can make a squeaking noise by rasping its beak across those ridges.

It is difficult to generalize beyond anatomy, but the wheel bug, Arilus cristatus, is a model of the typical assassin's life cycle. These 1-inch long insects get their name from a cog-like crest on their mid-section. By day they prowl slowly about trees, bushes and flowers, but strike prey with lightning speed. They can overpower insects many times their own size and weight. Pinning a victim with their front legs, they kill it almost instantly with an injection of toxic saliva. The potent cocktail of enzymes they deliver to victims approaches snake venom in virulence, dissolving the internal tissues into a soup that is sucked up by the wheel bug. A wheel bug may bite in self defense, too, or deploy red-orange scent sacs from its rear end.

After mating in the fall, female wheel bugs lay brown, bottle-shaped eggs in hexagonal clusters of 40 to 190. They cement them to tree trunks, fence rails, and other surfaces. Eggs on the periphery are vulnerable to tiny wasps that lay their own eggs inside them.

Those that survive hatch in early May. The nymphs lack wings, crests, or obvious sex differences. They go through five nymphal stages, each slightly larger than the last. To reach the next stage, they shed their exoskeleton, the skin-like outer cuticle. This process is called molting.

By early July, most larvae reach adulthood. They finally sport a crest and wings,

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