By Kathy Feagan
Assassin bugs are insects AND bugs (Insecta/Hemiptera order, Reduviidae family). Hemiptera are true bugs like aphids and stink bugs, which are considered to be ambush, predatory arthropods in the Insecta class. There are about 150 species of Assassin Bugs in North America. Here are three of the most beneficial.
Wheel Bugs (Arilus cristatus) are thought to be the largest Assassin Bugs in the U.S. They are gray to brown and grow to 1 to 1-1/2” long. Their distinctive crest at the top of the thorax (middle) gives them the Wheel Bug name. They have long legs as well as forewings and hind wings for slow, clumsy flying. They rely mostly on camouflaging, emitting scent, and their powerful bites for defense. Females are larger than males. Wheel bugs can be cannibalistic. After mating, females often kill and eat the male and nymphs eat each other. They are able to produce audible sounds by rubbing the tip of the proboscis (beak) against a groove under their thorox. These are very fierce predators, often attacking much larger insects including grasshoppers, cicadas, moths, beetles leaf hoppers, and caterpillars, as well as aphids, flies and bees. After trapping and grasping the prey with its forelegs, the assassin bug unfolds its long, tubular proboscis, then pierces prey and injects a toxin, paralyzing and dissolving tissues of, the prey. The Wheel Bug then sucks out and consumes all of the liquified fluids. These beneficials lie in wait for prey, well camouflaged, among flowers and leaves. Wheel Bugs are very common in most Texas gardens, among shrubs, fruit trees, crops and trees. They are most active during the day, hiding in leaves and debris. They are very attracted to goldenrod, cotton, decaying wood, sunflowers, locust and fruit trees. Wheel Bug adults have two red/orange scent glands, each of which serve a different purpose. One gland’s scent is used for defense and the other gland for breeding. The scent they produce is said to be not as noxious as a stink bug’s scent, but it is quite unpleasant.
Mating season begins in autumn. Females lay 40 to nearly 200 brown eggs in their short lifetimes, then die. She lays her hexagon shaped clusters of eggs on leaves of bushes, twigs, trees and plants. She secretes a glue to attach and protect the eggs. The eggs hatch in spring, after overwintering and emerge as tiny red nymphs. They then go through five instars/molts until they reach adult stage. Each molt takes 18-19 days with the final 5th instar being the very longest. The complete process takes over 90 days. Eggs hatch in May to June and these insects become adults, with their distinctive crest, in late summer, then die after mating and laying eggs. Nymphs are born predators, eating masses of insects between instars. Nymphs lack the ‘wheel’ of the adult, are wingless, and have bright orange to red abdomens. Adults can fly and make a loud buzzing sound when flying. Although they prey indiscriminately on beneficials and pests, most gardeners appreciate the wheel bugs since they eat so many types of destructive, non-beneficial bugs and insects, yielding a pesticide-free, vigorous landscape. They will bite if threatened or handled by people. Their bite is severely painful, with effects that are long lasting, and can produce days of numbness.
Leafhopper Assassin Bug (Zelus renardii) are very common here in Texas. They can be red-brown and yellowish-green in color and are ½ to 1” long. They are impressive predators of leaf-footed bugs, caterpillars, aphids, flies, mosquitoes, cockroaches, fleas, termites and boll weevils. They can eat up to 99% of the body weight of prey. They are very slender and use their stick-like forelegs to catch prey. Their front, spineless legs and the tip of their curved proboscis are coated with an adhesive substance that enables them to catch prey easily. They prefer gardens, flowers, fields and cotton crops. Leafhopper Assassins hide and ambush prey. They have a sucking, piercing proboscis that is used to suck the fluids of their prey. Leafhopper Assassins go through a three-stage life cycle of egg, nymph and adult (incomplete metamorphosis). The nymphs resemble tiny adults without wings. The nymphs become vigorous predators upon hatching and throughout their instars and molts. Females lay barrel shaped, sticky, dark brown eggs with a white cap in clusters on plants. They will give you a very painful bite if threatened or handled. The eggs hatch and evolve through five instars, from nymph to adult in about 2 months. Nymphs resemble Leaf-footed bug nymphs, allowing the nymphs to be closer to their favorite prey. The nymphs are small and bristly and have orange markings. They have multiple generations each year. Adults live for about two months. They are attracted to fruit trees, sage and passionflowers.
Milkweed Assassin Bugs (Zelus longipes) are very common here and are about 1” long. They are bright red to orange with black markings and have long, hairy black legs, antennae and wings. They look very similar in coloration to Milkweed Bugs which helps them camouflage from predators. They are very non-discriminating beneficial insects eating soft-bodied insects like milkweed bugs, aphids, flies, mosquitoes, roaches, beetles, caterpillars, stink bugs, tomato worms, bees, horseflies, armyworms and more. Their proboscis is orange with a black tip. They hide in foliage, and await prey. Their front legs are coated with a sticky substance, which the Milkweed Assassin secretes, aiding in holding their prey. The prey is then paralyzed when the Milkweed Assassin inserts the beak-like proboscis into the prey’s body. Enzymes are pumped in and the dissolved tissues are sucked out. They are able to capture and kill insects up to 6 times their size. They can bite if handled. Females lay clusters of 15 or more eggs upon upper leaves or stems of plants and shrubs. Females lay many eggs throughout the spring and summer. The eggs are brown and coated with a sticky, gelatinous layer with an opening for the nymphs to emerge. They develop from egg to adult in about 60 days. Nymphs have no wings, are less than ½”, changing from light brown to orange bodies and black legs as they mature. They can be found in fields, gardens, crops, weeds, trees, and grasses. Milkweed Assassins are very attracted to yarrow, which provides nectar and attracts prey. They can be seen perching atop vegetation, with their forelegs raised for ambush.
The Big Country Master Gardener Association presents free education programs every month. There is a program at 6:00 p.m. on the 1st Tuesday of the month at the Abilene Public Library South Branch in the Mall of Abilene, and the same program is presented again at 10:00 a.m. on the 2nd Friday of the month at the Abilene Public Library main location. We also have a Master Gardener Saturday Seminar from 9:00 a.m. to 12:00 noon on the last Saturday of the month from February through August in the Taylor County Extension Office Conference Room.
We are here to help you. If you have any questions, call the Taylor County Extension Office at 325-672-6048 or email us at bcmgardeners@yahoo.com. We hope you will visit our Facebook page, our website at bcmgtx.org, and the BCMGA YouTube channel for all Big Country Master Gardener information, events, and training.
Until next time… Happy Gardening!