University of Maryland Extension

Summer stingers – Eastern yellowjackets, Vespula maculifrons

Dr. Michael Raupp, Professor and Extension Specialist, Ornamental Horticulture, IPM

Recently, while mowing my lawn, I was jumped by a wicked band of furious yellowjackets that swarmed from their subterranean redoubt and delivered a couple of memorable stings to my ankle. As I danced away from the swirling storm, they sought retribution on my unfortunate lawnmower.

Yellowjackets are among the most aggressive of stinging insects found in Maryland. Unlike the European hornets, these gals seem to seek vengeance with little provocation. Several species of yellow jackets are found in the mid-Atlantic region. The ones nesting in my backyard were natives, the Eastern yellowjacket, Vespula maculifrons.

Females usually spend the winter in protected locations outdoors and start new colonies in the spring. Their colonies can be underground, within wall voids or man-made structures such as sheds or old cars, or in dense shrubs or vegetation. Nests are made of papery chambers that house developing brood and an outer shell of paper that encloses the comb. Unlike the nests of bees, the yellowjacket’s nest contains no honey or pollen. Yellowjacket larvae eat meat and carbohydrate rich foods provided by the workers. In this regard, yellow jackets are beneficial because they kill many caterpillars and beetles that are pests in our gardens.

Applesauce at a picnic makes a great snack for yellowjackets.

By late summer and early autumn, colonies may contain thousands of workers and are often about the size of a football. Under extraordinary circumstances, some nests may persist for more than one year and reach gigantic proportions. There are reports of monster yellowjacket nests in southern states reaching the size of a “Volkswagen Beetle”. Yikes! I sure wouldn’t want to bump into one of those with the lawn mower.

In late summer and autumn, new queens are produced in the colony and workers become manic in their attempts to gather enough food for the developing royals. Feisty workers are common around trashcans, fruit trees, and outdoor eateries where they gather protein from sandwiches and sweets from fruit or open cans of soft drinks. Be careful when you picnic. Look at a potential picnic spot and select a table or patch of lawn removed from trashcans that are sure to be buzzing with hungry bees and wasps. Yellowjackets often enter drink cans in search of sweets. These unseen guests can really liven up a soft drink, but swallowing one is dangerous. Instead of drinking from cans that may contain yellow jackets, use cups or clear bottles that allow you to see what is in your drink. Drink boxes with straws are a good choice for children to reduce their risk of imbibing a yellow jacket or bee.

If you encounter stinging insects at your picnic table, gently brush them away from your food rather than swatting them or flailing your arms. Quick aggressive movements on your part may be rewarded with the same by a yellowjacket. If you blunder upon a nest in the lawn or in a bush, walk away from the nest as quickly as possible with a minimum of swatting and arm waving. Walking through a bush (no, not one with the nest) may help throw the pursuing workers off your trail and help you escape without stings.

Yellowjackets love the sweetness of soda, and often slip inside cans for a nasty surprise!

When attacking, a yellowjacket releases a chemical signal called an alarm pheromone into the air. The pheromone signals other yellowjackets to attack and sting. Yellowjackets are capable of multiple stings. However, they have barbs on their stingers and many lose their stingers and internal organs when they attack. They sacrifice their life in defense of the colony.

If you know of a yellowjacket nest and the nest is unlikely to be encountered by humans or pets, you may simply leave it alone. If the nest is in a place that threatens you, children, or pets, you may consider eliminating it. Commercial pest control operators can assist you in this. I have purchased aerosol sprays, applied them according to the instructions on the label, usually at night or in the evening, and had excellent success. Please be careful around these fierce warrior wasps or you might get stung.

To learn more about a variety of insects, visit Mike Raupp’s Bug of the Week website. Bug of the Week thanks Dr. Nancy Breisch for sharing her expertise and knowledge about stinging insects.

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