Wednesday, June 13, 2012

Insect assassin: The wheel bug

    Not all the insects you can find in pecan tree canopies are harmful to your crop. Here's an example of a large insect predator that can be found searching pecan foliage for other insects to eat (photo at right). This large, grey bug features a pronounced "cogged wheel" protruding from its back and strikingly red antennae. Arilus cristatus is the largest member of the assassin bug family (Reduviidae) growing nearly 1.5 inches long.
    The wheel bug feeds on caterpillars, sawfly larvae, aphids, or any insect not fast enough to get out of the way. This insect has a long, red, tube-like mouth part that is normally held under the head.  When a wheel bug attacks another insect, it holds back its head then throws out its tube-like mouth parts like a javelin into the body of its prey. The wheel bug immediately injects a neurotoxin into the body of its victim, paralyzing it. Once the prey is immobilized, the wheel bug secretes its digestive fluids into the insect's body. After the insect becomes pre-digested, the wheel bug sucks all the fluids out through its tube like mouth parts.
    The wheel bug is one of our major predators of walnut caterpillar and fall webworm. But be careful around this beneficial insect. If you even get bitten by a wheel bug, the neurotoxin secreted in this insect's bite will leave a painful welt on you that can will last for days.