A Wheel Bug, an assassin bug, hangs out on a bronze fennel, which is the home of one of his favorite meals -- Black Swallowtail Caterpillars. This is a young Wheel Bug, which hasn't yet formed the characteristic wheel protrusion on its back.
Every day, I watch the progress of the Black Swallowtail (BST) caterpillars on my huge bronze fennel plant, which is home to a lot of other insects, including this character (see photo) who seemed to be hanging out and doing nothing while sitting on a fennel flower. Very suspicious. I thought he was up to no good. He gave me this look that said: “Hey, Lady, Don’t look at me. I’m just minding my own business.” Yes, exactly. What was his business? What did he eat? He wasn’t sipping flower nectar like the bees and wasps and occasional butterfly. I confess after a couple of days, I gave the fennel a shake and this bug tumbled to the earth. The next day I saw him slowly making his way back to the top. I don’t know how much I should interfere to protect “my” BST caterpillars. Was this a “good” bug or a “bad” bug?
I emailed Monarch Watch at the University of Kansas about this bug. Jim Lovett replied: “Looks like an immature wheel bug to me (Order: Hemiptera; Family: Reduviidae)…if you’re not familiar with this bug be sure to check out some images of the adult. It’s a neat little critter that always captures people’s attention – “little” of course is relative; adults wheel bugs can be 1.5 inches long. They use that piercing/sucking beak to puncture their prey (and can inflict a painful “bite” on us humans if mishandled). FYI – all hemipterans (the “true bugs”) have piercing/sucking mouthparts.”
I asked whether this bug would eat a BST caterpillar.
Jim’s answer: “Yes, it would. It is a common predator on caterpillars (and other soft-bodied insects) of all sorts.”
Here’s a link Jim suggested: Wheel Bug. The Wheel Bug is the largest member of the Assassin Bug family and is related to stink bugs. Mean and smelly! But useful, too, because they eat a lot of damaging caterpillars.
The next day, the Wheel Bug disappeared and so did a few of my smaller BST caterpillars. I hope Mr. Wheely didn’t eat my caterpillars!
To learn more about butterflies and caterpillars, click on Monarch Watch. My most recent post on raising BST and Monarch caterpillars is here: Survivor — Caterpillar Version.
Catherine Sherman 