COMMON SCENTS – BOX ELDER BUG INSTANT MESSAGING

(A follow-up on my Facebook post the other day showing spruce boughs festooned with bright red box elder bug nymphs)

I’m out walking Sylvia the puppy. It’s cooled off considerably from the last-gasp-of-summer heat wave of the past few days, but it’s still a lovely, fall-ish sunny day.

I notice a couple of small sun-lit spots on the lawn slapped with blotches of red: dense swarms of box elder bugs. One numbers at least 1,000; the other, maybe half that number. The two hordes are about three feet apart.

Sylvia spots them and follows her nose to the smaller group. When she’s about a foot away, they scatter, suddenly, haphazardly…and all at once. Their flight evenly dilutes the red spot, and within five or six seconds it’s gone.

Meanwhile, the larger swarm has not moved. But I watch—fully expecting wonder as usual—as those insects headed that way from the first group reach its perimeter. Then—mind you, I now have Sylvia firmly in tow several feet away—the second legion explodes in flight simultaneously just as the first had.

         I’d have expected one of the heralds to 
         shout "Run for your lives!" or at least
         wave its wings madly.

PHOTO: Timothy Ng

WHO CUT THE CHEESE?
Now, I can understand how the big, red, compound eyes of every single one of the box elder bugs in that first swarm may have caught sight, in the same instant, of the schnauzer colossus coming at them. They’re out of there; no communication needed.

But for the second swarm to have reacted identically, with no sensory input other than the approach of a few fugitives from the first group, begs the question: how do these little red-coats communicate?

I’d have expected one of the heralds to shout "Run for your lives!" or at least wave its wings madly, but it turns out box elder bugs don't do that. Instead, it’s quite likely a matter of scent—one which apparently disperses incredibly quickly.*

All this leaves open the broader question: how do other creatures do it? A murmuration of starlings, chased by a falcon, sloshing like pools of water across a pitching sky. A school of 10,000 of herring veering as one from marauding dolphins.

PHOTO: John Myers

I guess we’ll leave that investigation for a future post. That’s what it’s like with Nature; so many questions, so little time.

* FROM ANIMALDIVERSITY.ORG:
Adults and nymphs have a pair of scent glands located on the dorsal side of the abdomen that secrete monterpene hydrocarbons and may be used for communication. Boxelder bugs also have a pair of ventral abdominal scent glands through which males secrete an exocrine compound during copulation to stimulate or claim the female. It is speculated that males also use this secretion during confrontations with other males. Males are attracted to the odor secreted by females. Boxelder bugs have compound eyes and ocelli, which are believed to aid in perception of the environment along with antennae, the primary sense organs. There are no acoustic or vibrational signals used for communication. (Aldrich, et al., 1990; Bauernfeind, 2005; Millar, 2006)