Assassin Bug on a leaf, Zelus renardii

Beneficial Insect — Assassin Bug

Common Name: Assassin Bug

Genus Species: Zelus renardii

Assassin bugs, Zelus renardii, are beneficial insects that should be encouraged in your garden. There are around 150 species of assassin bugs in North America, most of which perform a service to the gardener and farmer. The insects prey on insect eggs, leafhoppers, aphids, larvae, boll weevils and others.

Assassin bugs are found in weedy or bushy cover during the warm summer months. They may be in wildflowers, especially goldenrod, towards fall. They are also common in woodland areas, hedges and along roads, fences and trails. The insects move slowly and are easy to spot.


Assassin bug adults and nymphs are slender, colorful insects, often blackish, reddish, or brown. They have long legs; a long narrow head, round beady eyes, and an extended, 3-segmented, needle-like beak. Nymphs are quite small, about 1/4-inch in length when they hatch. They grow to an adult size measuring approximately 3/4-inch.

Insects in this order undergo incomplete metamorphosis. Adults are poor fliers, and both adults and nymphs move rapidly when disturbed.


Assassin bug attacking a potato beetle.
Assassin bug attacking
a potato beetle.

All assassin bugs are predators; some species feed on insects while others feed on the blood of mammals. Insect-feeding species eat a wide variety of small to medium-sized insect prey including caterpillars, leafhoppers, other bugs, and aphids. They also feed on beneficial species such as lacewings. Nymphs and adults are often seen stalking or lying in wait for their prey, which they inject with venom once they have caught. Assassin bugs are common natural enemies on many plants, including row and tree crops.

  Life Cycle:

Assassin bugs, like other Hemipterans (true bugs like aphids, cicadas and leafhoppers), undergo incomplete metamorphosis with three stages — egg, nymph, and adult.

Assassin bug eggs.
Assassin bug eggs.

The assassin bug female lays eggs several times during the warm season. The eggs are oval and brown and are usually attached to the underside of a leaf. The larva is similar in appearance to the adults and have the same long body. They do not have wings and must go through four to seven instars or growth periods before they are adults. This takes approximately two months and then the cycle starts anew. The nymphs are prey to birds, large arthropods and rodents. The assassin bug adults overwinter in leaves, bark and debris.

  Assassin Bug Bites

As beneficial as they are in the garden, assassin bugs will bite if handled or disturbed. Their bite is not considered threatening, but it can be painful. The bite remains painful and swells and itches for a period afterward, much like a bee sting or a mosquito. It injects a toxin that some people are allergic to. Any excessive pain or swelling should be reported to your doctor.

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