The milkweed assassin bug, scientifically known as Zelus longipes, is a predatory insect commonly found in gardens and agricultural settings across southern North America, Central America, and South America. These slender-bodied bugs typically measure around one inch in length. They are easily recognized by their striking orange and black coloration, long black legs, and antennae. Both adults and nymphs are active during the day, often seen on various plants.
A Hunter’s Diet
Milkweed assassin bugs are generalist predators, feeding on a diverse array of insects. Their diet consists almost entirely of insects, making them valuable allies in pest control.
They prey on a wide range of common garden pests, including aphids, armyworms, leafhoppers, caterpillars, and small beetles. Other common targets include flies, mosquitoes, and larger insects they can subdue.
While they primarily target pests, they are not selective and may also prey on beneficial insects like ladybug and lacewing larvae, and small bees. They are particularly effective against destructive pests such as corn earworms, cabbage worms, mealy bugs, and cucumber beetles. They can take down prey up to six times their own size, though they generally prefer smaller prey.
How They Hunt
Milkweed assassin bugs are ambush predators, capturing their prey. They typically hide among foliage, waiting for an insect to come within striking distance.
Their raptorial front legs are equipped with a sticky, glue-like substance that helps them grasp and hold onto their prey. Once an insect is caught, the assassin bug quickly paralyzes it by inserting its specialized mouthpart, called a rostrum or beak, into the prey’s body.
The rostrum is a three-segmented, needle-like structure. After piercing the prey’s exoskeleton, the milkweed assassin bug injects digestive enzymes. These enzymes liquefy the internal tissues of the prey, allowing the bug to then suck out the dissolved contents, leaving behind only the empty exoskeleton. This process is known as extra-oral digestion.
Beneficial Garden Predators
Milkweed assassin bugs are beneficial insects for gardeners and farmers. By consuming insect pests, they contribute to natural pest control, reducing the need for chemical pesticides. Their presence in gardens helps maintain a balanced ecosystem, protecting valuable plants and crops from herbivorous insects.
They do not feed on plants. They pose no threat to humans or pets; however, if handled carelessly, they may deliver a painful bite as a self-defense mechanism.
This bite is comparable to a bee sting, causing localized pain, swelling, and redness, but it is not medically significant and no true toxins are involved. The benefits these insects provide in managing pest populations outweigh the risk of a defensive bite.