Yellow Jacket

Vespula spp., Dolichovespula spp.

Quick Facts

• There are 17 species of yellow jacket in North America, but the most abundant is the Western yellow jacket (Vespula pensylvanica), along with the “common wasp”(Vespula vulgaris) and the German wasp (Vespula germanica).
• Yellow jackets don’t really need a reason to attack. Without being provoked, they can strike at any time, anywhere, injecting venom into the skin of both humans and pets.
• Although they are disliked by people due to their aggressiveness and painful sting, the presence of yellow jackets in urban areas is beneficial, as they prey on insects that would otherwise damage vegetation. They are also important pollinators.
• Unlike bees, yellow jackets can sting multiple times without dying, which can be extremely dangerous for those allergic to their venom.
• Yellow jackets are social insects that live in large colonies. In 2013, a Florida entomologist found a huge wasp nest with more than 1 million wasps inside.

Appearance

The yellow jacket’s size ranges from 1.25 to 1.8 cm – workers are usually smallest while the males and queen are slightly larger. Their appearance also differs depending on the caste. The workers have alternating black and yellow bands on their abdomen, with the black bands much thicker than the yellow ones. The male yellow jacket has one thick black band near his thorax, but as it approaches its stinger, the black band starts thinning while the yellow band increases in thickness. The queen’s distinctive appearance is marked by a large black band on the back of its abdomen, followed by thinner black markings that go up to the dorsal end of its abdomen; there are two dots in-between the black stripes.

Females have a stinger at the gaster and are able to sting their victims repeatedly without losing their stinger (as it is not barbed, like in the case of honeybees).

Diet, Behavior & Habits

Yellow jackets are social insects that live in large colonies comprised of workers, males with a role in reproductions, and queens. Colonies are established once a year by a fertilized queen, which hibernates during winter in stumps, hollow logs, under leaf litter, and other such protected places, emerging from its hideout during late April or early May. As the “foundress” of the nest, she searches for and then selects a suitable nesting site in shrubs, tree canopies and holes, or inside manmade structures such as attics, under decks and porches, in hollow walls and flooring, in sheds, or under eaves of the roof. It is not uncommon for yellow jackets to build nests in soil cavities or mouse burrows.

The queen’s only purpose after building the nest is to lay eggs, quickly giving birth to the first generation of sterile female workers, but also to next season’s queens and males (at about halfway through the season). The colony continues to expand and can reach up to 5,000 workers and up to 15,000 brood cells, in normal weather conditions. However, a cold snap in the spring may kill all queens emerged before April, decimating the future nest’s population.

The diet of yellow jackets consists primarily of foods rich in sugar and carbs such as fruit and nectar, which they suck out of flowers with their highly developed tongue and strong mouthparts. They also need protein, which they take from meat and fish. The food is chewed and prepared into a paste to be served to larvae, which in turn secrete a sugary substance that will be eaten by adults – process named trophallaxis. During times when their regular food is scarce (summer and fall), they start scavenging for alternate food sources, and here is where the humans-yellow jackets conflict intensifies. They will land on anything sweet, including sugary drinks, sweets, juices, candy, but also rotten fruit, vegetables, meat, etc., disrupting any outdoor activities that involve food, such as picnics, barbecues, and summer parties.

In their quest to locate food sources, yellow jackets use their very fine sense of smell and eyesight. First of all, they are aided by sight to recognize flowers and potential prey such as insects and caterpillars. Then they guide themselves by smell towards a particular flower or tree branch. With the help of the pheromones they secrete, they are able to identify nest mates from enemies and rivals and also send each other signals regarding food sources, mating, and potentially dangerous situations.

Management & Control

Despite the fact that they make the most irritating company at picnics and summer parties, most social wasps, including yellow jackets, are actually extremely beneficial in the garden. They prey on caterpillars, flies, spiders, and other insects that would otherwise cause significant damage to fruit gardens and crops, so their presence should be encouraged in low-traffic areas. However, their services as predators and pollinators come at a price: keep the distance – a task oftentimes difficult, since they sometimes invade your space to build their nest. If you think the proximity to their nest is putting your wellbeing at risk, here is how to ensure proper management and control depending on the location of the colony:

Above ground nests: The method of choice for treating above ground nests is either with a powerful insecticide dust or a wasp spray (or a combination of both). During daytime, spray the insecticide in a fanning motion in order to repel soldiers and foraging workers returning to the base. Oftentimes, however, it is difficult to obtain instant results and eliminate the entire colony in one setting, that’s why it is best to contact a pest control company to handle these highly toxic substances efficiently. It is also the easiest way to avoid seeing the treated nest reactivating in a couple of days after a couple workers and brood manage to survive.

Underground nests: The entrance to the nest should be identified and correctly marked before applying the insecticide (preferably, a product labeled for yellow jacket control that has immediate effect). While it is indicated to apply the insecticide at night (when all foragers are inside), refrain from using flashlights, as wasps and yellow jackets are attracted to light. Introduce the dispenser nozzle toward the entrance to the nest and spray the product as indicated on the label. Very important: use protective gear – hat, veil, gloves, and coveralls – as wasps are probably going to turn aggressive if they sense their nest is being disturbed or in danger.

Individual yellow jackets: For individual yellow jackets that make their appearance to close to your family and house, trapping is the simplest method you can use to reduce the danger of being stung by one of these vicious creatures. Lure traps is a first solution: an attractant – usually heptyl butyrate – combined with one of their preferred foods – chicken meat or cake – are mixed and placed inside the trap. The traps should then be placed along the edge of the property and far away of any areas where children and pets are present. They are most effective at trapping western yellow jackets. Water traps, which also uses an attractive bait to lure the wasp into a 5-gallon bucket of water and cause it to drown, are quite effective at disrupting the activity of foraging workers.

Please note that no insecticide will guarantee 100% to annihilate all the yellow jackets on your property. Sometimes, even when using a spray that streams up to 20 feet, it is still possible to get stung by a partially intoxicated wasp that somehow managed to escape the nest. Especially in the case of underground nests, the actual colony can be located much farther away from the entrance, so the treatment may not reach all the members. Moreover, it is possible to encounter agitated and aggressive wasps in the proximity of the nest entrance even days after the insecticidal treatment. Contact your local pest control company to make sure all yellow jacket nests are removed safely and effectively.

Prevention

Yellow jacket and wasp stings are far more painful than those of bees and may produce local reactions or body-wide allergic reactions. People with allergic reactions to the venom may experience anaphylactic shock, and stings from multiple wasps can cause anything from intense pain and swelling to potentially fatal conditions. Here is how to stay out of yellow jackets’ reach:

• Keep sugary foods and ripe fruit in sealed containers
• Yellow jackets are also attracted to sweet drinks and may accidentally get into cans, so pour your drink into a glass to avoid getting stung
• Don’t swat at a yellow jacket that landed on you – gently blow air towards it or brush it off
• Wasps, hornets, and yellow jackets are very sensitive to smell, so don’t wear any perfumes or body lotions that may cause insects to mistake you for a flower (the same goes for floral prints and bright colored clothing)
• Keep garbage bins properly covered and sealed
• Don’t leave pet food out the whole day

Sometimes, to make sure your house and garden are not yellow jacket-friendly, here are some steps to take:

• Cover gaps, cracks, and crevices into the roof
• Seal holes in exterior surfaces that are likely to be treated as access points, such as chimneys, mortar seams, loose siding, and around windows and doors
• Install fly screens to doors and windows to prevent individual wasps from flying inside (usually attracted by the smell of food)
• Use weep hole fittings to avoid yellow jackets and other insects from entering your house through ventilation or drainage holes
• Clean your house and garden regularly. Lawns and vegetation should be trimmed periodically to deter insects from building nests nearby