Monday, August 5, 2013

My neighbors are wasps

Although I’ve lived next to lakes with sandy beaches for most of my life, I had no idea sand wasps existed until this summer. 

I became aware of them one day while sitting on a chair near the water.  When I gazed down, I noticed numerous wasps buzzing around the beach.  As I looked more closely, I realized the wasps weren’t flying randomly.  They seemed focused on precise locations.  A single wasp would land on a specific sandy spot and madly begin digging its way underground.  After a furious effort, it would disappear completely only to reappear moments later, fly away and then return to begin the process again.

The more I watched, the more fascinated I became.

A black and white striped sand wasp prepares to excavate its sandy burrow

My fascination increased when I saw one wasp return to the site with a caterpillar in its clutches.  The wasp inserted the caterpillar (which was almost as large as the wasp itself) into the tunnel.  It then proceeded to spread sand over the entry hole until it was impossible for me to tell where the tunnel had been.

Immediately, I thought of the potter wasps that I had learned about in July.  Potter wasps are solitary wasps.  The female builds a marble-shaped nest attached to a stick, wall or other surface.  When the nest is complete, she lays a single egg inside the nest and then drags in numerous paralyzed but still alive caterpillars for her larva to feed upon as it develops.  Once she has laid an egg and inserted a sufficient number of caterpillars into the nest, the adult wasp seals up the hole and lets nature take its course.  If all goes well, the developing wasp will dine on the inert caterpillars until it is ready to drill its way out of its single-celled home to begin the cycle anew.

A potter wasp in the process of building a nest

Because of what I knew about potter wasps, I figured I was observing a similar cycle with a different species of solitary wasps that nested on sand.  Eager to know more, I left the beach behind to seek information online.

What I discovered is that the insect I’d been watching is indeed a solitary type of wasp called Bembix speciosis, better known as a sand wasp.  Although I observed a sand wasp carrying a caterpillar, it mainly catches flies, stuffing its dugout nest with dozens of houseflies, deer flies and other annoying pests. 

Although the female is capable of stinging people (the male isn’t), she rarely does.  Like potter wasps, sand wasps are beneficial insects.  Not only do the adult wasps capture caterpillars and flies to feed to their young, they themselves feed on nectar, which helps pollinate flowering plants. 

Bembix speciosis is just under an inch long with large eyes, transparent tan wings and a black-and-white banded body and bright yellow legs.  Its elongated mouth doubles as a digging tool, which comes in quite handy when excavating a burrow, an occupation that takes up a considerable part of a sand wasp’s life.

Sand wasps don’t linger long in one spot.  These industrious insects are constantly coming and going as they build one nest after another (often close together).  Each deeply tunneled home – a tunnel can be 10 to 20 inches long - contains a single egg.  When the female wasp is not busy enlarging her burrow, she’s out hunting for food to fill it.  After each visit to her underground lair, the wasp seals the hole tightly to deter predators from finding her undeveloped offspring and its stash of food.

Despite her valiant efforts, most wasp larvae never make it to maturity.  Grub-seeking armadillos eat some and I’m sure I’ve inadvertently destroyed quite a few developing sand wasps myself when I’ve weeded the beach or dug holes in the sand with my grandchildren.  It’s not easy being a sand wasp.

Armadillos disturb many sand wasp nests in their search for grubs

Most of us could care less about wasps.  We lump together all potentially stinging creatures in one category:  Bad Bug!  Armed with cans of insecticide, we kill indiscriminately without hesitation, remorse or a sense of wrongdoing. 

But not all bugs that look scary are bad. 

In fact, insects like the sand wasp and potter wasp are among the good guys working hard to make our lives better.  If you see a large black-and-white striped wasp zooming around the beach sand this summer, don’t freak out, run away or reach for the Raid.  Sit back instead and watch the show.  You are privy to a flying marvel of maternal instinct, determination and indefatigable effort.   

The only sting you’re likely to get from this wasp is the sting of regret for all the times you’ve overlooked observing one of nature’s small wonders.

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