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Assassin bugs

Also known as Reduviidae, Wheel bug, Kissing bugs (a blood-feeding subgroup)

Beneficial or harmlessBeneficial
Assassin bug (Rhynocoris iracundus) with curved beak and long legs Photo: Charles J. Sharp · CC BY-SA 4.0

In short

Assassin bugs are long-legged predatory bugs that stab insects with a curved beak, inject paralysing saliva and suck them dry. They take caterpillars, beetle larvae, aphids and other bugs, so they are generally good to have. They also defend themselves with a very painful stab, so look but do not handle.

How it looks

Adults are about 5–36 mm long depending on species with a narrow, elongated head that looks like it sits on a neck, long legs, and a stout, curved beak folded under the head. Colours vary from grey and brown to black or boldly red, orange and black. The North American wheel bug is grey-brown, 25–38 mm, with a cog-shaped crest on its back. Nymphs are wingless, often brightly coloured or pale, and some cover themselves in debris or prey remains. Eggs are glued to plant surfaces; wheel bugs lay groups of barrel-shaped eggs on trees and shrubs.

Signs

A slow, stalking bug on foliage holding a caterpillar or beetle on its beak; empty prey carcasses.

Life cycle

Egg, five nymph stages and adult; usually one or two generations a year.

What favours it

Shrubs, flower beds and vegetable plots with plenty of insect prey; broad-spectrum sprays reduce them.

Prevention

  • Avoid broad-spectrum insecticides so these predators can persist.
  • Wear gloves when working in dense foliage and do not pick them up.

Treatment

Start with the first step and move down only if the problem persists.

  1. No control needed outdoors. If one comes indoors, move it out with a jar and card.
  2. If you are bitten and the reaction is severe or does not settle, seek medical advice.

Pros and cons

Pros

  • Eat caterpillars, beetles and their larvae, sawfly larvae, aphids and stink bugs.
  • Venomous saliva lets them kill prey larger than themselves.

Cons

  • A defensive stab is very painful — described as as bad as or worse than a wasp or hornet sting — and the area can stay numb for several days.
  • They also take honeybees and other beneficial insects.
  • A blood-feeding subgroup, the kissing bugs (Triatominae), transmits Chagas disease in Central and South America; garden assassin bugs are predators of insects.

Look-alikes

Plant bugs
Plant bugs have a straight beak held under the body and no neck-like head; they feed on plants.
Praying mantises
Mantises are larger, with folded, spiked front legs and chewing jaws.
Stink bugs
Stink bugs are shield-shaped with a broad, short head.

Where you find it

Outdoor shrubs, vegetables, flowers and trees.

Sources

  1. Assassin bugs — UC IPM Natural Enemies Gallery
  2. Reduviidae — Wikipedia
  3. Wheel bugs: good bugs with a painful bite — University of Illinois Extension

Written in our own words from these sources. Check a product label before using any treatment.