There are many bees and wasps that make their homes as beasties in our gardens. Yellowjackets are one of the few of the very large number of wasp species in western Colorado that live a social life.
Yellowjackets are sometimes mistakenly called bees, but they are actually wasps. Their mouthparts are well-developed with strong mandibles for capturing and chewing insects, with a proboscis for sucking nectar, fruit, and other juices.
In the United States there are eastern, prairie and western species of yellowjackets. The western, Vespula pensylvanica, is the wasp we deal with. They are the ground and cavity nesting one. These wasps tend to be medium sized and black with jagged bands of bright yellow on the abdomen and have a very short, narrow "waist," the area where the thorax attaches to the abdomen. They are smaller than a honeybee.
Concern about yellowjackets is based on their persistent, pugnacious behavior around food sources and their aggressive defense of their colony. Usually stinging behavior is most often encountered at nesting sites, but sometimes scavenging yellowjackets will sting if someone tries to swat them away from a potential food source. Their sting can be painful but these wasps are only a danger to those that have an allergic reaction to their venom.
Yellowjackets are social hunters living in colonies containing female workers, queens, and males. Colonies are annual affairs with only inseminated queens overwintering. Queens emerge during the warm days of late spring or early summer, select a nest site, and build a small paper nest in a cavity in which they lay eggs. After eggs hatch, the queen feeds the young grub-like larvae for about 18 to 20 days. Larvae pupate, then emerge later as small, infertile females called workers. Workers in the colony take over caring for the larvae, feeding them with chewed up meat or fruit. They also assume the tasks of nest expansion, foraging for food, care of the queen and larvae, and colony defense. Colonies can reach a maximum size of 3,000 to 5,000 workers.
Newly produced males and queens leave the parent colony in the late fall to mate. After mating, males quickly die, while fertilized queens seek protected places to overwinter. Parent colony workers dwindle, usually leaving the nest to die, as does the foundress queen.
The diet of the adult yellowjacket consists primarily of items rich in sugars and carbohydrates, such as fruits, flower nectar, and tree sap. Larvae feed on proteins derived from insects, meats, and fish, which are collected by the adults. Many of the insects collected by the adults are considered pest species, making the yellowjacket beneficial to agriculture.
The use of yellow lure traps is one method that can be employed to try to reduce yellowjacket problems.
I have two yellowjacket colonies in my garden rock walls. I find this insect fascinating to watch and have never been stung since I was a child. You will find that I have "a live and let live" attitude when it comes to beasties in my garden.