Tuesday, September 22, 2015


A Yellowjacket worker searches the forest floor for a meal for her and her nest mates.

     Yellowjackets (Vespula spp.) are social wasps who can be beneficial most of the year. They however often come in conflict with people, specially in the Fall. Because of their striped appearance, they are often confused with bees, and most stings are actually due to Yellowjackets rather than bees. They are more slender however, with the thin wasp waist, and normally not very hairy as compared to bees such as honeybees.
     Yellowjackets as adults feed on sugars, nectar, rotting fruit, and occasionally scavenge. They can be minor pollinators of some flowers, but just are not built for it since they do not need to collect pollen to feed their young. Instead, they feed their young proteins in the form of insects and spiders that they sting and bring back to their nests. In this manner, they can be beneficial in controlling some insect populations, though they will just as likely sting and kill a beneficial insect as they would any pest species. If their prey is too large, the wasps will bring it back in pieces or ingest it to regurgitate back to the nest's young later. For a video showing one trying to capture a large food item, please check out this short clip from the Capital Naturalist YouTube Channel:


     Yellowjackets are social insects, with a queen laying eggs and workers (her daughters) providing such labor as building and repairing the nest, foraging for food, and defense. Males (drones) are produced once a year in the Fall. After mating, the newly fertilized queens find a secluded spots underground or in old logs to overwinter. The males die soon after mating. The old queen and her workers all die also, at least in our part of the country.
     In the spring, the new queen awakens and goes out to search for a place to start her nest. She often picks an old rodent burrow or rotten log. While most nests are underground, they will occasionally find open spaces in walls or build an aerial nest (there's one species, Aerial Yellowjackets, that almost always do). The nest is constructed of wood fibers that are chewed into pulp and then made into paper building material. This she uses to make the nest and the cells she lays her eggs into.

What it would look like if you broke into a Yellowjacket nest.

         After the first generation, workers take over most duties, but the queen is the only one who lays eggs. By the end of summer, the large paper nest may be the size of a basket ball and have 3,000 or even more workers. Because these structures are hidden underground or in old wood, we rarely see them. For a look at an active nest, please check out this short video clip from the Capital Naturalist YouTube Channel:


The inside of a Yellowjacket nest revealing paper cells, larvae, and even some emerging new workers.

     On a steady stream of chewed up insects and spiders, the young quickly multiply. Because the nests are hard to see, people sometimes stumble upon them. Early in the season, there may not be many workers ready to defend the nest, but by Fall the numbers have swelled and the workers are more than willing to give up their lives in defense of their siblings and mother.
     Only females can sting, since the stinger is a modified ovipositor or egg laying apparatus. Males thus cannot sting. Females can do so repeatedly, injecting venom that can be painful and which they normally reserve for capturing prey. Predators include bears, skunks, and raccoons, though these often try and raid nests when it is cooler or stop their attacks early if the defense gets to be overwhelming. Since Yellowjackets do not produce honey, these predators are simply raiding to eat the larvae.
     When a worker stings, it tags whatever it has stung with a chemical marker that then targets the victim for any new wasp to sting. Once so marked, the female workers will attack their enemy relentlessly and will sometimes follow the perceived aggressor for quite a while before ceasing. This of course can lead to dangerous and painful situations, especially if someone is allergic to their stings.
     I happen to be someone who was allergic to Yellowjacket venom (though thankfully not to other stinging insects such as bees or paper wasps). In my case, I use to get stung numerous times a season. Though it hurt, I was not too worried about them. One day however, I was stung in the ear while at work at a nature center. After getting some ice and complaining to my coworker, I started feeling dizzy and then blacked out. I awoke in an ambulance and getting a rash and hives. After getting stung so often, though over time, my body had finally had enough getting envenomated. I had to go through a desensitization program of weekly injections until I had built up my resistance to their stings once more and still have to carry an epipen just in case. Interestingly, that was many years ago and I have not been stung since. I have a sixth sense it seems now in seeing their nests and avoiding them.

A Yellowjacket worker enjoys a sugary drink from a bottle cap.

     In the Fall is when we have most negative encounters. Not only are the nests large and there are more workers, but their behavior changes a bit too. Yellowjackets throughout the summer had to bring back food for the young and work to keep their nests in good shape. This included repairs, expansions, and keeping them dry. Workers of paper making nests have to sometimes drink excess water to keep the nest from getting destroyed after rains for example.
    By Fall however, new reproductives are being produced, the new drones and queens. There are fewer larval mouths to feed and many workers helping to do this. Many Yellowjacket workers thus go for the easiest food they can find. While their preference for sweets is usually satisfied with rotting fruit and nectar, many discover easy food near trash cans, picnics, and from our sodas and sugary confections.
     While I must say that I certainly am not crazy about Yellowjackets (and have every reason I think to not like them), I respect them and understand that they're beneficial and have a role in our natural world to play. I just take extra caution in my outdoor activities, especially this time of year.

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