Thursday, July 16, 2015

Jeff Michals-Brown: Wasp Watcher

Well-equipped Wasp Watcher on a baseball field:
Bag with water and sunscreen--CHECK
 Vial of alcohol (for preserving beetles, mind you)--CHECK
Indiana Jones hat set at a fashionably rakish angle--CHECK

I am now an officially trained Wasp Watcher.  I will spend a few hours each day or so from now to early August monitoring colonies of Cerceris fumipennis wasps in their preferred habitat: nearly bare, hard-packed sandy soil like that around a slightly down-at-the-heels baseball diamond. 

Why, you ask, would I want to stand in the hot sun for hours at a time watching wasps?  It's part of a nifty trick called biosurveillance.  The wasps are, in fact, working for us; and I am watching to see what beetles they bring home.

 Cerceris burrows look like ant hills with over-sized openings.
Soil is piled up evenly all around, and the hole is big enough to put a pencil in.

"Smoky-winged beetle bandit," wasp is the common name tentatively given to Cerceris fumipennis.  The yellowish band around the base of the abdomen is easy to spot, but not diagnostic: Cerceris fumipennis has look-alike relatives.  The real McCoy also has three yellow spots on its face.

You can be sure you have the right wasp when you see it enter or leave its burrow!
NOTE: the wasps are on the small side, and don't seem able to sting humans.

The "wrong" wasp, digging the "wrong" hole: 
notice the soil is almost all to one side.

It started for me a year ago when the majestic white ash in my back yard took sick.  Leaves yellowed and fell all summer and fall until it was bald before its time.  So I did what anyone frantic with worry would do: I turned to Google.  I quickly turned up the Mother of all ash killers: the Emerald Ash Borer.  The EAB is an invasive alien beetle from Asia which probably came into this country accidentally--like so many alien invasives before it.  It was discovered in Michigan and nearby Canada in 2002, after being imported in packing materials, probably years before.  The beetle has spread rapidly, reaching a point north of Boston just last year.  The ash trees that evolved with the EAB in Asia can usually survive an infestation, but all ash trees on this continent die.  The adult beetle eats ash leaves, causing little damage, but the beetle larva bores under the bark; the damage to the bark usually girdles the tree and kills it in a matter of months   I watched my tree anxiously for signs of beetle infestation.  The good news: my tree didn't have them; it was sick with something less serious.  The bad news: the Emerald Ash Borer was spreading unchecked, and was expected to eventually eliminate ash trees wherever in North America they were.  The EAB was recently ranked the most destructive insect in the country.  My tree, currently in the bloom of health, is doomed--so is yours.

Sadly, we have aided the Emerald Ash Borer in its spread.  On their own they might migrate a few miles in the space of a year; at that rate, we should have had many years to deal with the problem.  However, if the larvae happen to burrow into a trunk that later becomes firewood, and someone transports that firewood to another place, the beetle spreads astronomically faster.

What does the wasp, Cerceris fumipennis, have to do with this?  The wasp is a good card-carrying native, and harmless to humans.  But it is a fierce predator to certain types of beetles: those wood-borers of the family Buprestidae, called Jewel Beetles.  It stings the beetles, and carries the paralyzed insects back to its burrow to lay its eggs on.  The wasp is good at catching beetles, and Wasp Watchers are good at catching wasps.  In effect, the wasps are sampling the local beetle population, and doing it far more effectively than we can.  We need only confiscate some of the beetles to find out who's out there.  The collected beetles go on to experts who will identify them. In short, we are putting wasps to work finding us invasive wood-boring beetles.

Although the EAB isn't hard to identify, collecting all those beetles may give us an early heads-up on the next invasive--maybe early enough to eliminate or control it.  North America has already lost its chestnuts to chestnut blight, most of its large elms to Dutch elm disease, and it's rapidly losing ashes --some of the most majestic forest trees remaining.

I don't want to lose any more.

I hope to God not to find a half-inch long, narrowly oval, metallic emerald green beetle among the wasps' prey.  But if I don't find any this year, I'm sure I will next.

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