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
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
Insects in this order undergo incomplete metamorphosis. Adults are poor fliers, and both adults and
nymphs move rapidly when disturbed.
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 laying 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.
Assassin bugs, like other Hemipterans (true bugs like aphids, cicadas and leafhoppers),
undergo incomplete metamorphosis with three stages — egg, nymph, and adult.
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 are 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.
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.