Leave assassin bugs to their work

For the past two weeks, my email inbox has been flooded with the exact same question from several readers: “What is this crazy insect I found in my yard?” They go on to describe the insect as prehistoric, enormous and ugly. I've also been sent several pictures for identification.

I'm not surprised. Until a few years ago, I'd only heard of this insect, but I had never actually seen one in my 20-plus years of gardening. I knew they lived in our region, but they were so few and far between that most gardeners seldom ever had the chance to see one in real life.

Now, however, it seems they've become quite common. So far this summer, I've spotted a half dozen wheel bugs (Arilus cristatus) in my garden, and if you've ever had the pleasure of spotting one, you know it's not an insect you'll soon forget.

Wheel bugs are among North America's largest true bugs, reaching over an inch and a half in length at maturity. That's a crazy-big bug for Western Pennsylvania! And not only are they huge, their body looks like it's straight out of a science-fiction movie. Wheel bugs have half of a large “cog wheel” sticking out of their back and slender legs that make them move in a very robotic fashion.

But, despite their terrifying appearance, I'm here to assure you that they are very, very good for the garden.

You see, wheel bugs are a member of the assassin-bug family (Reduviidae), a group of several dozen different species. Gardeners most often encounter other, slightly smaller and more “normal-looking” family members, including the spined assassin, the masked hunter and several other species.

All assassin bugs use their front legs to ambush and capture prey insects, which they then pierce with their long mouthpart. They inject the insect with a lethal toxin, killing it within seconds. The same toxin then liquefies the captured insect's internal organs. The assassin bug then consumes its victim, leaving only the empty exoskeleton behind.

Wheel bugs and other members of the assassin family feast on lots of common garden pests, including hornworms, Mexican bean beetles, Colorado potato beetles, leafhoppers, cucumber beetles, lygus bugs, aphids and caterpillars of all sorts. Mind you, these predators will occasionally capture a ladybug or bumblebee along the way, but, overall ,they are on the right team, working to control many common pests.

Personally, I think the reason wheel bugs in particular are becoming so numerous here in the eastern United States is because they love to feast on the invasive brown-marmorated stink bugs that have become quite prolific in our region. I even spotted a wheel bug clinging to the back of my house with a stink bug in its grasp, using its long, curved mouthpart to suck the little stinker dry.

Though wheel bugs are “good guys” in the garden, you should be aware that, if handled roughly, their mouthpart can puncture human flesh and will leave a nasty, painful welt. If you're lucky enough to find one, leave them be and thank them for the work they do on your garden's behalf.

Horticulturist Jessica Walliser co-hosts “The Organic Gardeners” at 7 a.m. Sundays on KDKA Radio. She is the author of several gardening books, including “Attracting Beneficial Bugs to Your Garden: A Natural Approach to Pest Control” and “Good Bug, Bad Bug.” Her website is www.jessicawalliser.com.

Send your gardening or landscaping questions to tribliving@tribweb.com or The Good Earth, 503 Martindale St., 3rd Floor, D.L. Clark Building, Pittsburgh, PA 15212.