Beware of carnivorous yellow jackets

For those of us on the Kenai Peninsula, July and August is the time of year to stock up on salmon. Most of us plan on eating our fresh, canned or smoked salmon immediately and throughout the coming year. However, whenever I am processing fish, a swarm of pesky interlopers seem to arrive for a portion of the catch — yellow jackets that appear out of seemingly nowhere to aggressively buzz around the filleting table.
Yellow jackets are predatory wasps that feed on sweet, sugary substances, as well as on meat. The adults most often feed on sugary things, like sap or flower nectar. But right about now is when they are actively feeding their growing larvae in the nest and are best fed on proteins.
This explains why they can be seen around your flower garden, as well as anywhere there might be fresh meat available. If we weren’t so obliging with our fish cleaning, yellow jacket workers would be scouring the vegetation for insect larvae and adults they can capture, chew up and feed the youngsters. Because of their insect-hunting behavior, yellow jackets are actually a benefit to gardeners. (I know this is sometimes difficult to remember when they are buzzing all around your picnic table.) Later on in the summer, as the days turn colder and there are fewer larvae to feed in the nest, workers will predominately feed on sugary or carbohydrate foods.
In the late fall, the workers and drones die off. Fertilized queens overwinter under brush or in underground cavities. Summers following a particularly cold winter will have fewer surviving queens and fewer hives. Harsh winters in Arctic regions make it difficult or impossible for queen overwintering. However, a couple years ago, the very first yellow jackets were found above the Arctic circle. If the Arctic warming trend continues as predicted, the entire state will soon get to know these aggressive wasps.
In the spring, the queen starts forming a nest in a hidden area. Most often the nest is underground, but perhaps it will be in a hollow tree or other protected area, like under the eave of a building. The brood comb is made of chewed-up wood fiber, and eggs are deposited inside. The color of the comb will be determined by what kind of wood is chewed up, and will vary from light gray to a rich brown.
After 18 to 20 days and a lot of larval feeding, the new yellow jacket workers emerge. Soon the workers take over all of the duties around the hive, like foraging for food, making new brood comb and protecting the nest. Around mid-July, the hive will have hundreds of workers and the numbers can grow to several thousand individuals. This explains why they become so abundant at this time of the summer.
Yellow jacket wasps are often mistaken for honeybees, but can be distinguished because they have no hairs on their body and abdomen. Bees have noticeable hairs on their bodies and legs. Yellow jackets also always have a white or yellow face, while a bee’s face is dark. The alternating yellow and black abdominal stripes are thought to be a warning to birds and others that this is an insect that is not to be trifled with. Many birds avoid wasps and bees because of the possibility of getting stung. Those birds that target stinging insects like yellow jackets will often rub the insect’s abdomen on a limb in order to break off the stinger before swallowing it.
Interestingly, there are a number of Dipteran flies that can be seen around our flower gardens that have the same yellow and black stripes on the abdomen. The stingless flies gain some protection by looking like an aggressive and stinging wasp. You can tell the mimic by looking for the large eyes on the fly and its ability to hover without much wagging back and forth. This type of copycat coloration is known as Batesian mimicry.
What bothers most people is the fact that yellow jackets can inflict a painful sting. When the nest is disturbed by a possible invader, the workers swarm around the creature and will chase the retreating invader. A yellow jacket’s abdominal stinger has no barbs, like those of a honeybee, so it can sting many times without losing its weapon.
For some people, that sting can be more than a painful reminder of getting too close to the nest, it can cause a deadly reaction. Some folks have powerful immune responses to the venom, to the point of an anaphylactic reaction. Anaphylactic reactions can cause life-threatening swelling in the throat and laryngeal areas.
There are a number of people who have died in Alaska over the past couple years after being stung by yellow jackets. If you or a loved one reacts strongly to insect stings, your physician will probably want to prescribe, and you will want to carry, a self-contained “Epi Pen.” These may buy you the time to get to definitive medical attention after a sting.
I am personally allergic to honeybee stings and develop heavy swelling a day after the sting. Recently I stepped into a depression that turned out to be a yellow jacket’s nest, so I was very lucky to only get stung once. My allergy to honeybee stings apparently does not include yellow jacket stings, since I hardly swelled more than a mosquito bite. This personal anecdote points out that allergies vary individually and can be very specific or very general. As a side note, I do carry an Epi Pen, just in case.
There are at least 11 species of yellow jackets in Alaska and they seem to be found throughout much of the state. Though not usually welcome around people, remember that yellow jackets are not trying to disrupt your outing, but are probably just looking for a meal for their young.

David Wartinbee, Ph.D, J.D., is a biology professor at Kenai Peninsula College’s Kenai River Campus. He is writing a series of columns on the biology of the Kenai River watershed.

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Posted by on Jul 30th, 2013 and filed under Outdoors. You can follow any responses to this entry through the RSS 2.0. Both comments and pings are currently closed.

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