Birth of an Assassin Bug!

— Written By

The wheel bug, Arilus cristatus, is North Carolina’s largest assassin bug. It gets its name from the prominent spiny “wheel” found on the thorax. Both nymphs and adults are generalist predators that feed on a variety of insects including aphids, caterpillars, bugs, beetles, and more. The bug uses its stout beak to inject the prey insect with a toxin that kills it within 30 seconds. Most of their prey are pest insects so they are considered beneficial to farmers and gardeners. They move slowly and are clumsy fliers. Their bite has been described as being more painful than a wasp sting so they should be admired but not handled.

Adult wheel bug feeding on a Japanese beetle.

Adult wheel bug feeding on a Japanese beetle. Photo by Debbie Roos.

The wheel bug has one generation per year and lays eggs in late fall, usually on the branches of trees and shrubs. The eggs resemble miniature brown bottles. The eggs overwinter and the nymphs hatch from April-June. It takes the nymphs about three months to develop through five different stages before the final molt into an adult.

I spotted this egg cluster in early November last year and kept my eye on it this spring, watching for signs of activity. I was fortunate to be able to observe the nymphs hatching! They pop the top of the egg off then slowly emerge, unfurling their super-long antennae and legs. They emerge a bright yellow-orange color then quickly change to red and black. Their appearance changes slightly with each molt. Such a cool process to witness!

Wheel bug eggs on holly branch.

Wheel bug egg cluster on holly branch. Egg masses are usually found within four feet of the ground. This one was spotted in early November. Photo by Debbie Roos.

Wheel bug eggs on holly branch.

Wheel bug egg cluster on holly branch. Photo by Debbie Roos.

Close-p of assassin bug eggs.

Close-up of assassin bug eggs. Photo by Debbie Roos.

The nymphs are bright yellow-orange when they hatch in the spring. They quickly turn bright red and then darken as they molt. Nymphs do not have the distinctive wheel or crest of the adults.

Wheel bug nymph just starting to emerge from its egg.

Wheel bug nymph just starting to emerge from its egg. Photo by Debbie Roos.

Wheel bug nymph emerging from its egg. Photo by Debbie Roos.

Wheel bug nymph emerging from its egg. Photo by Debbie Roos.

Wheel bug nymphs emerging.

Wheel bug nymphs emerging. Photo by Debbie Roos.

Wheel bug nymphs emerging. Photo by Debbie Roos.

Wheel bug nymphs emerging. Photo by Debbie Roos.

Wheel bug nymphs emerging. Photo by Debbie Roos.

Wheel bug nymph emerging. Photo by Debbie Roos.

Newly emerged wheel bug nymph. Photo by Debbie Roos.

Newly emerged wheel bug nymph. Photo by Debbie Roos.

Newly emerged wheel bug nymphs.

Newly emerged wheel bug nymphs. Photo by Debbie Roos.

Newly emerged wheel bug nymphs.

Newly emerged wheel bug nymphs. Photo by Debbie Roos.

Wheel bug nymph feeding on a Colorado potato beetle larva.

Wheel bug nymph feeding on a Colorado potato beetle larva on eggplant. Photo by Debbie Roos.

Written By

Photo of Debbie RoosDebbie RoosExtension Agent, Agriculture - Sustainable / Organic Production (919) 542-8244 debbie_roos@ncsu.eduChatham County, North Carolina
Updated on Jun 12, 2018
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