Wheel Bugs

The racy photograph above of two mating wheel bugs was posted by Jessie Haworth to our Facebook page.  This seems like a good opportunity to revisit a 2010 post on this assassin bug member that looks like it crawled out of a science fiction movie.

The above adult wheel bug (Arilus cristatus) is easily identified by the gear-like armor on its back.  Like all true bugs the mouth parts (mandible, maxilla and labium or lips) have evolved into a piercing beak, called a rostrum or proboscis. It carries it tucked up below its thorax until swinging it out to stab into an unfortunate prey.  Unlike the Tiny Biter in the last blog, this bug can put a real hurt on you with severe pain followed by numbness for several days.

Many other true bugs, (Hemiptera for you Latin speakers), such as cicadas, aphids, planthoppers, leafhoppers, and shield or stink bugs use their beaks to suck plant juices.  Predatory species are equipped with specialized tools to inject their enzymes into their prey like an external stomach, then sucking in the predigested meal.  The mandible of some have tooth beaks (stylets) to cut into prey as well.

Assassin bugs have strong front legs which tightly grasp their prey as they stab their beak into it and inject digestive juices.  After these have done their work they are able to suck out their dinner like a high protein milkshake.  Most other insects which use this external digestion process have two tubes, one to inject and one to suck out the contents.  Reduviidae have just one large tube to inject and then slurp up the feast.

Empty egg case - Tonya Smith

Wheel bugs are a member of the Reduviidae family, aka assassin bugs.  They are mostly patient ambush hunters, waiting for an opportunity rather than chasing down prey.  Reduviidae go through an incomplete metamorphosis in which the first nymph (instar) that emerges from the egg has a resemblance to the eventual adult it will become.  The first instar of the wheel bug has a bright red back (picture from Bugguide) which is quite distinctive while the latter instar (pictured above) shows graying much like we humans.  

Assassin bug larva - Patrick Coin

The final stage of adulthood bring them their wings and sex organs.  This is similar to withholding the driving permit from a teenager as their hormones hit high gear.
Wheel bugs tend to move in a jerky motion, and their brief flights produce a loud buzzing sound.  They may bite humans who handle them, an extremely painful experience producing an open sore that can take months to heal.  If that isn't enough to dissuade you from picking one up, their "bad gas" problem may be.  They have two orange glands beside the anus that eject a foul scent when they are disturbed.

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