Southwest Environment

Stories written by University of Arizona students

Department of Soil, Water and Environmental Science
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The assassin bug preys on lygus

By Ben Beal

assin bug

Photo by Alan Moore. Some rights reserved.
The assassin bug (Zelus renardii) presents a great threat to other insects with its fold-out sucking beak and relatively imposing size.
One major predator of lygus in cotton is the assassin bug (Zelus renardii). If the name is not enough to convince you of its prowess, perhaps its appearance and arsenal of adaptations will. This bug is at the top as an “apex” predator, meaning almost nothing else preys on it.

The assassin bug is a red-brown or even yellowish-green color and grows to be about half or three-quarters of an inch compared to the lygus at about a quarter of an inch. Their relatively large size helps them prey on a variety of pest insects as well as some beneficial insects. In addition the legs of the assassin bug are covered in a sticky substance which helps them hold and capture their prey.

The assassin bug is a true hunter, lying in wait for its victims to come within its deadly range. Once the assassin has captured its meal, it pierces its prey with its straw-like beak, injecting digestive juices into the victim and sucking out the partially digested insides.

Even in its early nymph stages of life the assassin bug is an effective predator. During the nymph stages the bug is simply wingless and not fully grown. It will experience four molting stages before reaching adult size, and at every stage it is an effective predator.

The assassin bug is an insectivore and has no damaging effects on crops. It may be the top predator of insects in cotton crops, but it is more susceptible to pesticides than the lygus bug. When crops are sprayed with insecticide, caution must be used in order to avoid killing such an effective and beneficial predator as the assassin bug.


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