Queens stop laying eggs and nesting in general, in late summer and autumn. For this reason, the wasp's dietary needs change from a focus on protein sources (other insects which they usually eat) to a greater interest in collecting sweets and other carbohydrates. Some wasps may become aggressive scavengers around human food -- this is why they are common at picnics or around windfallen apples in orchards.
What are the benefits of wasps?
Wasps, especially European paper wasps, eat some of the insects in your garden that you might consider pests, such as hornworms, cabbageworms, tent caterpillars and aphids. Sawfly larvae are also tasty snacks for wasps.
Let's toast those European hornets and paper wasps for another reason! They tend to bite grapes while they're still on the vine and kickstart fermentation. Wasps often carry the yeast Saccharomyces cerevisiae in their guts, and this is the common brewer's yeast responsible for wine, beer and bread fermentation. When the wasp bites the fruit, some of the yeast remains in the fruit.
And, wasps inadvertently perform some pollinating services as well. The following excerpt is taken from The Encyclopedia of Life:
"An interesting relationship exists between yellowjackets and the broad-leaved helleborine (Epipactis helleborine), an orchid native to Europe but introduced in the eastern United States. The yellowjacket lands on the labellum (the showy, lowest petal) and drinks nectar. While doing so, it bumps its head on the anther and pollen becomes glued to the yellowjacket's head. To prevent the yellowjacket from grooming itself and potentially causing the pollen to become dislodged, some of this plant's nectar is converted to ethanol. This causes the yellowjacket to become intoxicated and to behave sluggishly. While in this state, the yellowjacket is less likely to groom itself and thus leaves the pollen on its head. During its next floral visit, the yellowjacket inadvertently deposits pollen onto the flower, thereby pollinating it. Yellowjackets have also been known to nectar from, and likely pollinate, common rhododendron (Rhododendron ponticum), squash (Cucurbita spp.), common milkweed (Asclepias syriaca), field garlic (Allium oleraceum), and field pussytoes (Antennaria neglecta)."
Why do wasps sting?
Wasps (and bees) only sting as a defense mechanism. If they feel threatened, they will sting. Yellowjackets adamantly guard their nest entrances, so vibrations and rapid movement, such as that caused by a lawn mower, can easily induce a sting. Some species release an alarm chemical upon stinging, which causes other wasps to join the attack. Thus, being aware of the location of a wasp nest is beneficial! Social wasps (those that live in colonies) do not die after stinging, as honeybees do, and thus, they can sting repeatedly.
How to avoid stings?
In recreation areas, be aware of wasps around waste bins, and check your food or drink before consumption. When in wasp-infested areas, avoid wearing sweet-smelling colognes, perfumes, or hair sprays. Wasps are attracted to bright orange, yellow, and blue clothing. Khaki, tan, and dark colors are less attractive to wasps. If a wasp does approach you, it is best to remain still or move away slowly, because rapid movements, such as swatting, may stimulate stinging.
So please do your gardens a favour, and discourage the use of those glass bell jars that are hung out to catch and kill wasps and other insects.
University of Minnesota Extension: Wasp and Bee Control by Jeffrey Hahn, Phil Pellitteri, Donald Lewis
NPR Food Blog: The Salt Thank the Simple Wasp For That Complex Glass of Wine
Oklahoma State University Extension:Paper Wasps, Yellowjackets, and Other Stinging Wasps by Hal C. Reed, Richard Grantham, Russell Wright
Colorado State University Extension: European Paper Wasp by W. Crenshaw
Encyclopedia of Life
Pictures: (Top) Northern paper wasp, and (Botom) detail showing paper wasp nest,
