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Wasps

When most of us think of wasps, we are really thinking about members of the Vespidae family, the colonial wasps. They are the most common and the ones we most often notice. According to David and Norma Barr, "There are only three main kinds of vespid or colonial wasps in North America... yellowjackets, paperwasps and the Bald-faced Hornet. Unfortunately, these common names have become hopelessly mixed up through local usage."

Yellowjackets

Yellowjacket can be "any of the 20 or so North American species of small, bright yellow-and-black wasps that build almost perfectly spherical paper nests either in cavities underground or (less frequently) hanging from a tree branch attached only by a narrow stalk at the top."

Yellowjackets are most commonly sighted during late summer and fall when food sources decline and the worker wasps — now numbering in the thousands and no longer busy in their colonies — spread out over backyards, picnic sites, and anywhere else they sense available food. At this time of year, they also seem more aggressive and unpredictable. Even so, "their pest status is limited only to a few weeks in late summer and fall, and at that time the chance of multiple stings is not great."

At the FWG, we didn't notice yellowjackets at all until early September when we were working in our Butterfly Meadow. Several volunteer have inadvertently disturbed an underground nest while weeding there and have been stung badly. The stings are quite painful and itch for days to weeks afterward.

The nest at the left was discovered in our Old Field, right on the ground. It's quite large - almost 30 cm in diameter.


Bald-faced hornets

Bald-faced hornet (Dolichovespula maculata) is "a larger, chunkier version of the yellowjacket but with the lighter coloured areas of the body cream to almost bone white; builds large shapeless paper nests in trees or bushes, almost always with several branches and numerous twigs woven through the body of the nest for support."

In 2006, we found three bald-hornet nests at the FWG. (We typically see only one large one each year.) One was in a shady area, about 2 metres above ground in an apple tree. One was in a pine tree (about 3 metres up) on the south side of the Ash Woodlot. The third, and largest, was only half a metre off the ground in a young Amur Maple tree in the field on the north side of the Ash Woodlot.

Paper wasps

Paper wasps (Pollistes sp.) are "an elongate, narrow, slow-flying and bumbling darker wasp with long spindly legs and dominant body colours of black, brown and amber; nests above ground in unprotected paper combs suspended in a sheltered location on the underside of a rock or a tree cavity and especially under the eaves of buildings; never surrounds the comb with a paper envelope."

At the FWG, we've seen two species of paper wasp: Pollistes fuscatus (below left) built a number of the typical umbrella-shaped nests in our garden shed this year (bottom left); P. dominula (below right) took up residence in the sign marking the beginning of the Bill Holland Trail. In September, we found one small P. dominula nest in the shed (bottom right).







The German yellowjacket

Adding to the confusion is a yellowjacket lookalike called the German Yellowjacket (Vespula germanica), which became established in Canada only in the 1960s (Barr and Barr 1981). It is more inclined to nest in cities and suburbs, and will use the inside walls of buildings, attics, and even the "joist space between a floor and the ceiling below." It remains "active in the fall much longer than most North American yellowjackets" and is considered somewhat more aggressive. If you have to have a wasp nest removed, you should call in a professional.

Potter or mason wasps (Eumenes sp.)

Potter wasps are solitary. The adults feed on flower nectar and collect small caterpillars to feed their young. The caterpillars are paralyzed by the wasp's sting and stuffed into compartments that the wasp builds out of clay. The female wasp then lays an egg on the stored caterpillars. The potter wasp larva consumes 1 to 12 caterpillars as it grows, making potter wasps important in the natural control of caterpillars.

The species of potter wasp we have noticed at the FWG constructs tiny round clay jars with a narrow neck. We've found these on the underside of milkweed leaves (above), on Queen Anne's lace flowers, and on the inside wall of our garden shed (right).



Mud daubers

Mud daubers are also solitary wasps. They construct small nests of mud in or around homes, sheds, and barns. At the FWG, we often find nests, which look like blobs of mud, under the eaves of our Interpretive Centre. The one at the left is about 7 cm long and contains 4 or 5 cells. These wasps are long and slender with a narrow, thread-like waist. Some are a solid blue-black, but others have yellow markings.

A female mud dauber collects mud, rolling a small amount into a ball and carrying it to the nest site. There she forms the mud into tubes - usually several side by side. When the mud is dry, she captures insects and spiders to stuff into the tubes, depositing a single egg on top before sealing each tube with more mud. The eggs hatch, the larvae consume the prey, and eventually become adults.

Wasps — the gardener's friend

If we need any other incentive to rethink our attitude toward wasps, the Barrs note that they are one of our "strongest allies in the ongoing biological control of leaf-feeding insect pests in the garden. One colony of native wasps in the backyard can produce hundreds of workers which, over the summer, take a tremendous toll of flies, caterpillars, grasshoppers and other backyard pests." And remember, only the females are equipped to give a painful jab, so a backyard nest of yellowjackets does not mean mass stingings.

Reference

David and Norma Barr. The garbage wasps. In Seasons, Summer 1981.


This page was revised 6 April 2013
© Fletcher Wildlife Garden
Text and photos: Christine Hanrahan and Sandy Garland
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