Owning a garden means making sure that you’re up-to-date with the types of insects that may choose to take up residence within the plants you’re trying to grow. Today, we’re talking all about the insect known as the Milkweed Assassin bug. Finding these insects is not a difficult task. Believe it or not, assassin bugs can live in a range of habitats ranging from your garden to a grassy meadow. Chances are, even while hiking through the forest, there’s a good chance you’ll find one of these brightly colored bugs searching for their next meal. If milkweed assassin bugs are practically commonplace amongst areas we frequent, it’s probably safe to assume that you’d want to know if they bite and, if so, will that bite be dangerous?
The short answer is: yes, they are capable of biting humans, but receiving a bite is unlikely. In the event that you are on the receiving end of an assassin bug bite, expect to feel a sharp pain that can result in a stinging sensation, swelling, and redness. Assassin bugs and their red and black color truly live up to their name. These skilled predators are adept in the art of hunting their prey. On a normal day the process involves laying a sticky trap and then hiding nearby for an unexpecting aphid or fall armyworm.
Like most insects, life begins forming within an egg. These extremely tiny clusters of vial-shaped eggs are laid by an adult and left to hatch on their own. Hatching eggs ushers in the nymphal instar stages. These stages summarize the process in which the insect is still adolescent, growing and molting repeatedly, but not quite considered an adult bug. The last stage is the adult stage.
Two you’re likely to meet in your garden are the wheel bug (Arilus cristatus) and the milkweed assassin bug (Zelus longipes). Milkweed bugs, Oncopeltus fasciatus, are reddish orange insects with a conspicuous black band across the middle and two large diamond-shaped black patches fore and aft. They are 1/2 to 3/4 inch long. Female milkweed bugs lay 25 to 35 eggs per day in small clusters. Eggs are light yellow but turn reddish before they hatch five days later. The nymphs emerge as tiny, elongate, red insects that soon become oval in top view. The nymphs develop and grow through five molts. Adult bugs emerge from the fifth molt. Nymphs become increasing spotted as they develop and their wing buds become more pronounced with each molt. New adults are yellow with black markings, but the yellow parts change to reddish-orange as they mature. Adults can mate a week or so after the last molt, and a week to two weeks later, females start to lay eggs. Females that have plenty of milkweed seeds available lay considerably more eggs than females on short rations. Once a new generation of adults matures, milkweed bugs migrate to sheltered spots to spend the winter, spring, and early summer.
Photo by J.R.
If the milkweeds infested with milkweed bugs are grown as food plants for monarch butterflies it may be better to live with the damage to the seeds rather than apply an insecticide. Milkweed bugs do little plant damage and are present for only a month or so. Remove leaf litter and spent stalks in the fall to eliminate overwintering sites. If the presence of the bugs is repulsive and no monarch butterfly caterpillars are present, use an insecticidal soap to kill the bugs as the dried residue of insecticidal soaps is not particularly toxic to caterpillars that might hatch shortly. If the milkweeds are not part of a butterfly garden, any of the various insecticides labeled for landscape use should give more than adequate control. Publication date: Nov. Reviewed/Revised: Nov. Recommendations for the use of agricultural chemicals are included in this publication as a convenience to the reader. The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsement by NC State University or N.C. A&T State University nor discrimination against similar products or services not mentioned. Individuals who use agricultural chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage regulations and examine a current product label before applying any chemical. For assistance, contact your local N.C. N.C. Bug of the Week is written by "The Bug Guy," Michael J.
In the lexicon of entomology, the term true bug identifies a large and important order of tens of thousands of insect species known as the Hemiptera. Hemiptera, the true bugs, are characterized by their sucking mouthparts and incomplete metamorphosis consisting of egg, nymph, and adult stages. Many true bugs are plant feeders, including harlequin bugs, squash bugs, and stink bugs we met in previous episodes, but many are fierce predators playing an important role annihilating pests of crops and ornamental plants. I bumped into the first of these assassins on the leaves of an herbaceous plant. The milkweed assassin bug, Zelus longipes, has a diabolically clever strategy for catching its prey. Hiding in foliage with its forelegs outstretched, it awaits the approach of an unsuspecting victim. The front legs of this assassin bug are coated with sticky goo (a technical term) perfect for snaring a victim. Once captured, the prey is impaled with a hungry beak that injects proteolytic enzymes, which predigest the contents of the victim.
In recent episodes we met blister beetles, ambush bugs, and longhorned beetles feeding and hunting prey on flower heads of goldenrod. Another spooky denizen of goldenrods and other meadow plants is the orange assassin bug, Pselliopus barberi. Why this bug sports a costume of orange with black stripes is known only to Mother Nature and other orange assassin bugs. I watched this stealthy assassin move slowly about a goldenrod blossom with a small leafhopper skewered on its beak. How it was able to sneak up and stab a highly mobile and wary leafhopper is known to the assassin bug but is a mystery to me. The third amigo in this triad of terror is the large assassin bug known as the wheel bug, Arilus cristatus.
We met wheel bugs and learned of their important role as biological control agents of the brown marmorated stink bug in previous episodes of Bug of the Week. In addition to dining on invasive pests, this generalist predator has a taste for native protein sources including several types of caterpillars. In autumn the female wheel bug deposits clusters of barrel-shaped wheel bug eggs on the bark of many types of trees. The following spring when prey return to pester plants, the eggs hatch into gorgeous orange nymphs. The thorax of the nymphs soon changes from orange to black, but as nymphs grow and molt, a reddish-orange color is retained on the abdomen until full adulthood.
Like other assassin bugs, the business end of the wheel bug is the powerful beak, or proboscis, stored between the beast’s front legs when it is not in use. Upon spying a tasty morsel, the wheel bug cautiously approaches, embraces the prey with long front legs, and then impales the victim with its powerful beak. The wheel bug pumps strong digestive enzymes through the beak into the prey. These enzymes liquefy the body tissues of the hapless victim. A muscular pump in the head of the bug slurps the liquefied meal up through the beak.
Tiny wheel bug nymphs enter the world orange and yellow but soon the head and thorax darken to black. An older nymph impales a hapless lightening bug and skulks to the edge of a leaf to drain the beetle’s blood. ReferencesThe informative publication “Milkweed assassin bug (suggested common name) scientific name: Zelus longipes Linnaeus (Insecta: Hemiptera: Reduviidae)” by Megha Kalsi and Dakshina R. Seal was used to prepare this episode. Like most true bugs, members of the assassin bug family have membranous wings that fold flat along the back when at rest (often creating an X pattern on the back) and strawlike mouthparts specialized for piercing and sucking. Assassin bugs are a very large group with diverse body forms, but most are black or brown (sometimes orange, yellow, or red) with a rather oval body. The head is usually narrow and the antennae long, thin, and often jointed. All have a clawlike beak with 3 segments that can fold into a groove beneath the insect’s body. The first segment on the first pair of legs is usually thickened, and the sides of the abdomen often extend beyond wings. Similar species: Leaf-footed bugs (family Coreidae) are commonly mistaken for assassin bugs. Most leaf-footed bugs have flattened, leaflike extensions on their hind legs. Leaf-footed bugs are plant-eaters. Assassin bugs are good flyers and walkers. They prowl around trees, gardens, and grassy areas, hunting other insects. Most people consider them beneficial, as they help control many insect pests. Handling assassin bugs is not recommended, as they can inflict a painful bite. They sometimes land on people but can be brushed off easily, if they do not soon fly away on their own. Like many other true bugs (such as cicadas, aphids, stinkbugs, and leafhoppers), assassin bugs have strawlike mouthparts adapted for sucking nutrients - in this case, it’s the juices of other insects. (One group of assassin bugs sucks blood.) Much like a single-fanged spider, an assassin bug bites its prey, delivering a venom that subdues its insect prey and causes its tissues to liquefy. People who have been bitten by assassin bugs probably are not in love with them. But to the gardener, the farmer, and anyone else “bugged” by insects, the assassin bug is a friend. Invertebrates are animals without backbones, including earthworms, slugs, snails, and arthropods. Arthropods-invertebrates with “jointed legs” - are a group of invertebrates that includes crayfish, shrimp, millipedes, centipedes, mites, spiders, and insects. There may be as many as 10 million species of insects alive on earth today, and they probably constitute more than 90 percent all animal species.
Figure notes: The olive-orange coloration, predation strategy, and lifecycle details are typical of Zelus longipes and related Hemiptera. Be mindful of identification cues when observing in the garden.
Images and supporting visuals can help distinguish Zelus longipes from similar predators in the yard.
Wheel bugs serve as examples of powerful predatory design and role in biological control.
Identification and Visual Cues
Milkweed assassin bugs are bright orange with long, spindly black legs. They are easily recognized in the garden as common Florida predators that resemble a bright, warning color warning to potential threats. The wheel bug, Arilus cristatus, is another conspicuous predator with a cog-like crest across its back, making it one of the easiest beneficial bugs to identify in North America.
Biology and Predatory Mechanisms
Assassin bugs have a powerful beak or proboscis stored between their front legs when not in use. Upon striking, they inject toxins that paralyze prey and liquefy tissues, which the bug then suctions up. This predatory method mirrors a sequence where prey is captured, envenomated, and liquefied for consumption.
Lifecycle and Development
Life begins with eggs laid by an adult, often in clusters. Hatching leads to nymphal instars, during which the insect molts several times before reaching the adult stage. In many assassin bug species, the nymphs start orange or yellow and progressively darken as they molt, with wing buds becoming more pronounced toward maturity.
Distribution and Habitat
Assassin bugs inhabit a range of habitats from gardens to grassy meadows and forested areas. Florida is highlighted as a region where milkweed assassin bugs are particularly common, alongside other species such as the wheel bug that thrive in similar environments.
Host Plants and Garden Interactions
Milkweed plants can harbor milkweed bugs that assist in pest control but may cause seed damage in monarch butterfly gardens. If monarchs are a priority, gardeners may tolerate some seed damage to benefit pollinator networks; otherwise, milder controls such as insecticidal soaps may be considered, bearing in mind non-target effects on caterpillars that may hatch later.
Lifecycle Details: From Egg to Adult
Eggs are laid in clusters, often on plant surfaces or bark, and hatch after a few days. Nymphs pass through multiple molts, changing color as they mature, until the adult emerges. Adults mate after final molts, and the cycle repeats with new generations.
Behavioral Notes and Human Interaction
Assassin bugs are generally beneficial garden allies, helping control pests. They can deliver a painful bite if handled or threatened, though such bites are not normally medically dangerous for healthy individuals. They are capable flyers and walkers, often approaching gardens in search of prey.
Practical Considerations for Gardeners
To minimize overwintering sites, remove leaf litter and spent stalks in the fall. If you want to limit milkweed bugs without harming monarchs, insecticidal soap can be used, though it is best to reserve such controls for situations where monarch caterpillars aren’t present. When in doubt, rely on integrated pest management strategies that favor natural predators and habitat diversity.
You Can’t Unsee the Assassin Bug’s Dirty Work | Deep Look
Related Species and Comparison
Two other notable orange-red assassin bugs in gardens include Pselliopus barberi and the wheel bug, Arilus cristatus. These species share predatory habits and contribute to pest suppression in various plant communities.
| Species | Color/Identification Cues | Predatory Role | Common Habitat |
|---|---|---|---|
| Zelus longipes | Bright orange body, long black legs | Preys on aphids and caterpillars | Gardens, meadows, fields |
| Arilus cristatus | Gray to brown body with wheel-like crest | Predator of caterpillars and beetles | Trees, gardens, borders |
| Pselliopus barberi | Orange with black stripes | Predatory on various garden pests | Meadow and garden blossoms |