Western Yellowjacket – Vespula pensylvanica

Western Yellowjacket– Vespula pensylvanica
Bees & Wasps Index | Bees & Wasps Main | Aculeata – Bees, Ants, and Stinging Wasps
Live adult yellowjacket wasps photographed at Arkansas River near Buena Vista, Chaffee County,
Colorado, USA. Size: 15mm

Western Yellowjacket – Vespula pensylvanica Taking on water at the headwaters of the Arkansas River

Yellowjackets are considered quite beneficial to agriculture since they feed voraciously on agricultural pests, but they become a nuisance when they scavenge for food at picnics or other outdoor venues where food or sugary beverages are served. Many are attracted in large numbers to garbage cans, others fly in and out of nests built around homes, buildings and areas where people live.

One simple way to avoid attracting yellowjackets and wasps to your soda cans is to serve only diet beverages, that is, those that don't contain sugar. These gals have no interest in liquids that don't contain sugar. I don't know what to do about the lunchmeat, however. They be liking salami!

Eastern yelowjacket leaving underground nest
Eastern yellowjacket leaving underground nest

My dad once asked me to eradicate a nest right next to his back door, and I very reluctantly agreed. The wasps were entering and leaving their underground colony via a hole in a railroad tie landscape timber. Well, kids, this turned out to be a gigantic nest of wasps, despite it modest entrance. A can of Raid flying insect spray later, my dad and I had both been stung multiple times, and those yellowjackets were VERY riled up.

When a colony perceives itself under attack, all the wasps in attendance pour loads of alarm pheromones into the air, telling each other to attack moving objects in the vicnity. As workers return from foraging in the field, they get a whiff and hurry to help. A very efficient system that works automatically, an army without a leader; this is an organism controlled by chemicals. They use chemicals to communicate and each individual processes its actions according to the pheromones present. It is by individuals obeying a small number of rules very consistently that the colony achieves complex behaviors like nest-building and progeny-rearing and mutual defense. A worker has no choice when assailed by alarm chemicals: she immediately begins to emit the same chemicals and turns her attention toward identifying the intruder. Her actions throughout her life consists of very rigid responses to chemicals emitted by her nestmates, the larvae she tends, enemies, and especially her queen.

It is by such simple rules the birds in a flock create such lovely twisting designs in the air – how is it the individuals in the flock are able to so quickly communicate a change of direction to its neighbors? They are not talking to each other, "Hey! turn left when I tell you!" There is no leader per se. There is only one rule each individual must obey: "Maintain a specific distance from the others." Every bird becomes simultaneously a leader and a follower.

Yellowjackets don't have barbs on their stingers like honeybees. They'll grab onto your clothing and just keep stinging you until you get the picture and swat them to the ground – and it takes a healthy swat, too. The stings were very painful and itched and burned for days afterwards, and that nest lived on and prospered for the rest of the year.

Yellowjacket Wasp
Compare to: Eastern Yellowjacket – Vespula maculifrons

Yellowjackets are social wasps living in colonies containing workers, queens and males. Colonies are annual with only inseminated queens overwintering. Fertilized queens occur in protected places as hollow logs, in stumps, under bark, in leaf litter, in soil cavities and human-made structures. Queens emerge during the warm days of late April or early May, select a nest site and build a small paper nest in which eggs are laid. After eggs hatch from the 30 to 50 brood cells, the queen feeds the young larvae for about 18 to 20 days. Larvae pupate, emerging later as small, infertile females called workers. By mid-June, the first adult workers emerge and assume the tasks of nest expansion, foraging for food, care of the queen and larvae, and colony defense.

From this time until her death in the autumn, the queen remains inside the nest laying eggs. The colony then expands rapidly reaching a maximum size of 4,000 to 5,000 workers and a nest of 10,000 to 15,000 cells in August and late September. At peak size, reproductive cells are built with new males and queens produced. Adult reproductives remain in the nest fed by the workers. New queens build up fat reserves to overwinter. Adult reproductives leave the parent colony to mate. After mating, males quickly die while fertilized queens seek protected places to overwinter. Parent colony workers dwindle, usually leaving the nest and die, as does the founder queen. Abandoned nests rapidly decompose and disintegrate during the winter. Nests inside structures will persist as long as they are dry. Nests are not used again.

In the spring, the cycle is repeated. (Weather in the spring is the most important factor in colony establishment.) Although adults feed primarily on items rich in sugars and carbohydrates (fruits, flower nectar and tree sap), the larvae feed on proteins (insects, meats, fish, etc.). Adult workers chew and condition the meat fed to the larvae. Larvae in return secrete a sugary material relished by the adults. (This exchange of material is known as trophallaxis.) In late autumn, foraging workers (nuisance scavengers) change their food preference from meat to ripe, decaying fruit.

My admiration for these industrious creatures knows no bounds and I have no doubt they will be around long after we are gone.

Order Hymenoptera: Bees, Wasps, & Ants

Hymenoptera (Latin for membrane wing) is a vast assemblage of insects second only to Coleoptera (beetles) in the number of described species. Hymenoptera number some 115,000 species – of which 18,000 live in North America. Hymenopterans inhabit a wide variety of habitats, and show an incredible diversity in size, behavior, structure and color.
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