Assassin bugs
Assassin bugs are true bugs in the family Reduviidae, with roughly 160 to nearly 200 species in North America north of Mexico, depending on the source. They are predators: they stab caterpillars, beetle larvae, aphids, leafhoppers and other bugs with a curved, three-segmented beak and inject saliva that liquefies the prey. They also eat bees, lady beetles and lacewings, so they are not selective. Most are good to have in a garden, but they bite if handled or crushed, and the bite is painful. Brush one off rather than slapping it.
At a glance
- Kind
- Wild — conserved, not bought
- Size
- 1/5–1½ in (5–38 mm), by species
- Species
- About 160–200 in North America
- Eats
- Caterpillars, beetle larvae, bugs — and bees
- Life cycle
- Egg, five nymph stages, adult; usually 1–2 generations a year
- Bite
- Painful if handled or crushed
How it works
An assassin bug hunts by ambush or by slow stalking. It sits still on foliage or creeps up on prey, then stabs it with a hinged, needle-like beak that folds into a groove under the body. The saliva it injects subdues the prey and liquefies its insides, which the bug then sucks up. Adults and nymphs look alike: long legs, a narrow head on a distinct neck, and long antennae. Nymphs have wing pads instead of full wings. The eggs are laid in rows or clusters of 10–70, shaped like little flasks with ornate caps, and cemented upright to plants.
Assassin bugs pass through five nymphal stages and typically have one or two generations a year; Clemson says most species have only one. Zelus species usually overwinter as adults, and the orange assassin bug shelters as an adult under loose bark. Most garden species are ½–¾ inch long, such as the ½-inch spiny assassin bug, and the largest is the wheel bug at up to 1¼–1½ inches. The kissing bugs (Triatoma) are also assassin bugs, but they feed on blood instead of insects; see the lookalikes below.
What it is confused with
Most people who look up assassin bugs have either been bitten or want to know whether the long-beaked bug in the garden is a pest. These are the insects most often confused with them.
- PestKissing bugs (conenose bugs) — Blood-feeding assassin bugs, ½–1 inch long, most with orange or red stripes around the edge of the body and a straight beak tucked underneath. Their bite usually does not hurt, unlike a garden assassin bug's. Chagas spreads through their droppings, not the bite; Texas A&M will identify one from a photo.
- PestLeaf-footed bugs — Plant-feeders with flattened, leaf-like flaps on the hind legs. Their nymphs have dark legs and antennae; young Zelus assassin bugs, which look similar, have pale ones.
- Also goodWheel bug — The largest assassin bug in North America, up to about 1½ inches, grey to brown, with a cog-like crest on its back. It belongs to the same family, hunts the same way, and its bite stays painful for several minutes.
- Also goodAmbush bugs — Small, well-camouflaged bugs that wait for prey on flowers. They used to be placed in their own family but are now counted as assassin bugs.
How to keep it around
Nobody needs to buy assassin bugs for a garden, because they arrive with the insects they eat. Keeping them is mostly a matter of not killing them.
- No broad-spectrum insecticides, which is Maryland Extension's first advice for keeping assassin bugs
- Flowers and plants that draw a wide variety of insects, the assassin bugs' prey
- Trees, garden beds and grassy areas, where they prowl and hunt
- Loose bark left on trees over winter, where species such as the orange assassin bug shelter as adults
- Gloves for summer weeding and pruning, because crushing or slapping at an assassin bug is what generally makes it bite
Pesticide sensitivity
Broad-spectrum insecticides kill assassin bugs along with the pests, and Maryland Extension's advice is to avoid them. None of the sources read gives product-by-product toxicity for this family. Open the compatibility matrix →
When to choose something else
Assassin bugs are background help, not a targeted control. Look elsewhere when:
- You need one pest gone — none of the sources read measures how much assassin bugs reduce damage in a garden, so count them as a bonus
- It is leaf-footed bugs on tomatoes or pomegranates — hand-pick them, and let the tachinid flies work
- The problem is spider mites — ARBICO, which sells leafhopper assassin bug (Zelus renardii) eggs, says not to use them alone for mites; use Phytoseiulus persimilis
- You want to buy some — ARBICO sells Zelus renardii eggs, but it cannot ship them to 31 states, DC or Puerto Rico, and the wild ones are free
- The bug has orange or red stripes around the edge of its body — send a photo to Texas A&M's kissing bug program before assuming it is a garden assassin bug
Assassin bugs by target
What it eats and when it turns up differ by pest. Each page below is the picture for one target.