Yellowjackets, commonly known as "meat bees," in comparison to the "vegetarian" honey bees, will be among the wasps featured at the Bohart Museum of Entomology's open house from 1 to 4 p.m., Sunday, Sept. 25 in Room 1124 of the Academic Surge Building, 455 Crocker Lane, UC Davis campus. The theme: "Weird and Wonderful Wasps."
The open house is free and family friendly. A family arts and crafts activity is also planned.
"Yellowjackets are social wasps that build large, hidden nests," writes Lynn Kimsey, director of the Bohart Museum and a UC Davis distinguished professor of entomology, on one of her online fact sheets. "The nests are usually subterranean in rodent burrows or in cavities in trees, walls or attics.
"Yellow jacket nests can be huge with 50,000 to 100,000 workers," Kimsey points out. "In temperate climates these colonies are annual. Their nests die in the fall after producing new queens. New queens produced by the colonies in the fall spend the winter in protected places until spring when they found new colonies. Yellow jacket colonies can become perennial in warmer climates, such as in Hawaii and coastal California. In these situations the nests can become enormous, with millions of workers!"
Kimsey says that yellowjacket nests "can be distinguished from paper wasp nests because the brood cells are encased in a paper envelope so they can't be seen without taking off the outer envelope. These wasps generally feed on live prey, but the pest species, such as Vespula pensylvanica, will scavenge other sources of meat and sugar, including sodas, hamburgers and road kill. They will also visit aphids and scale insects for honeydew."
At the open house, visitors will learn about the smallest fairy wasps to the "murder hornets"; what role wasps play in plant galls and figs; and how to distinguish a parasitoid from a parasite. Kimsey will discuss the Asian giant hornet, Vespa mandarinia. A single colony of the Asian giant hornet was found and destroyed Sept. 18, 2019 in Nanaimo, Vancouver Island, Canada, and a single dead hornet was found Dec. 8, 2019 in nearby Blaine, Wash. Since then, it also has been sighted-- and destroyed--in both Canada and Washington state.
Fairy wasps, in the family of chalcidoid wasps, are tiny insects. They include the world's smallest known insect, with a body length of only 0.139 mm (0.0055 in), and the smallest known flying insect, only 0.15 mm (0.0059 in) long, according to Wikipedia. The fairy wasps are found in temperate and tropical regions throughout the world. The family contains approximately 100 genera with 1400 species. All known fairy wasps are parasitoids of the eggs of other insects, Wikipedia says, "and several species have been successfully used as biological pest control agents."
Dec. 22 marked the winter solstice, the first day of winter.
But don't tell that to the western yellowjacket, Vespula pensylvanica.
It's supposed to be hibernating, not flying.
But there it is flying around--and sipping nectar--from flowering Algerian ivy climbing a fence in Vacaville, Calif.
It has company. Nearby, several other yellowjackets, honey bees and hover flies are participating in the nectar feast.
Not much is blooming this time of year!
So, what is winter solstice? According to the Farmer's Almanac, "Winter solstice is the day with the fewest hours of sunlight during the whole year. In the Northern Hemisphere, it always occurs around December 21 or 22. (In the Southern Hemisphere, it is around June 20 or 21.)"
Now the days are getting longer.
Is it spring yet?
A recent visitor at a camp in the Sierra Nevada mountain range witnessed a large number of wasps and stinging behavior. They crowded around the picnic tables (ah, meat!) and sipped from soda cans (ah, sugar!) She wondered if they were yellowjackets or European paper wasps.
From the description and behavior: yellowjackets.
"European paper wasps (Polistes dominula) are not scavengers," says Lynn Kimsey, director of the Bohart Museum of Entomology and a professor of entomology at UC Davis. "They only take live insects, particularly caterpillars. Western yellowjackets, Vespula pensylvanica, are serious scavengers and are major pests in the Sierra and elsewhere. Their colonies are annual, which means that fertilized new queens must overwinter in protected places until it warms enough in the spring to begin new colonies. As the new colonies are building they need a lot of protein for their babies. The larger the colonies get the more they need."
"If many new queens survived the winter because temperatures were warmer and drier than usual then there will be many colonies to deal with, all competing for food. By late in the season the colonies go more into maintenance mode, needing a lot of sugar. They aren't feeding many babies, which need protein, and the large number of adults need sugar for fuel."
"At this point, control is largely useless," Kimsey says. "Control measures need to be started in the mid to late spring and the best control method is the use of baited traps, not spraying. Also when colonies are found they need to be removed--this needs to be done at night. These wasps nest in cavities, mostly in the ground but also in attics, wall voids and hollow trees if available. The large number of stings suggests that a colony or colonies were nearby."
"So at this point it's best to hope for a long cold, wet winter," Kimsey says.
The UC Statewide Integrated Pest Management Program (UC IPM) provides a wealth of information on Western yellowjackets and paper wasps on its PestNote: "In Western states there are two distinct types of social wasps—yellowjackets and paper wasps. Yellowjackets are by far the most troublesome group, especially ground- and cavity-nesting ones such as the western yellowjacket, which tend to defend their nests vigorously when disturbed. Defensive behavior increases as the season progresses and colony populations become larger while food becomes scarcer. In fall, foraging yellowjackets are primarily scavengers, and they start to show up at picnics and barbecues, around garbage cans, at dishes of dog or cat food placed outside, and where ripe or overripe fruit are accessible. At certain times and places, the number of scavenger wasps can be quite large."
"Paper wasps are much less defensive and rarely sting humans," according the to the UC IPM PestNote. "They tend to shy away from human activity except when their nests are located near doors, windows, or other high-traffic areas."
The UC IPM authors point out that "Typically, previously mated, overwintering yellowjacket and paper wasp queens begin their nests in spring when the weather becomes warm. The queen emerges in late winter to early spring to feed and start a new nest. From spring to midsummer, nests are in the growth phase, and larvae require large amounts of protein. Workers forage mainly for protein at this time—usually other insects—and for some sugars. By late summer, however, the colonies grow more slowly or cease growth and require large amounts of sugar to maintain the queen and workers; foraging wasps are particularly interested in sweet things at this time. Normally, yellowjacket and paper wasp colonies live only one season. In very mild winters or in coastal California south of San Francisco, however, some yellowjacket colonies survive for several years and become quite large."
UC IPM has posted an informative YouTube video, "Distinguishing Between Yellowjackets, Wasps, and Look Alikes." Look closely and you can see that those European paper wasps have distinctive orange antennae. Yellowjacket antennae are black.
Or, to put it another way: Yellowjacket antennae are black, like the Oakland Raiders' logo, and European paper wasp antennae are orange, like the logo of the San Francisco Giants.
Last weekend a little critter made its first-ever appearance in our family bee garden. It was neither a grand entrance nor a grand insect.
"A fly!" I thought, as I looked at its knoblike bristle or arista on the end of each antenna.
But its body--what little I could see of it before it winged out of there--definitely resembled a wasp. A Western yellowjacket (Vespula pensylvanica) or European paper wasp (Polistes dominula).
Native pollinator specialist Robbin Thorp, emeritus professor of entomology at the UC Davis Department of Entomology and Nematology, identified it as a syrphid fly, genus Ceriana, family Syrphidae.
Talented Davis photographer Allan Jones captured an excellent photo of Ceriana in 2012. A full body shot: head, thorax and abdomen! His excellent image (second one, below) shows the distinguishing characteristics: two wings (fly), not four wings (bees, wasps), as well as the arista (fly) and the spongelike mouthparts (fly).
BugGuide.Net posted some excellent images of Ceriana on its site. Class: Insecta. Order, Diptera. Family: Syrphidae: Genus: Ceriana.
Ceriana is a genus of wasp mimics. Basically, it's a syrphid fly, a pollinator. It's also known as a hover fly or flower fly as it hovers, helicopterlike, over flowers before drops down to forage.
Would-be predators, no doubt, avoid Ceriana because of its coloration. "Oops, don't mess with that! That's a wasp!"
Picnickers who don't know a faux wasp from a real one would probably run from it, or swat at it.
"It's definitely a good mimic and probably gets a lot of protection from that coloration," said Lynn Kimsey, director of the Bohart Museum of Entomology and professor of entomology at UC Davis.
The question begged for an answer.
"It's yellowjacket time again. Does anyone have or recommend a good trap?"
A Bay Area beekeeper today sought recommendations from ledEric Mussen, Extension apiculturist with the UC Davis Department of Entomology and Nematology.
Mussen, who recently co-authored "Yellowjackets and Other Social Pests" on the UC IPM website with Michael Rust of UC Riverside, responded candidly.
"There are a number of ways that people try to deal with populations of yellowjackets at this time of year," he told her.
- If you can find the nesting area, a whole colony can be dealt with, directly.
- If you can’t find the nest, then most people resort to trapping, since putting out poisonous baits no longer is legal. You can purchase the yellow plastic traps at hardware and nursery stores, etc. You can catch quite a substantial number of wasps, but that often does not alleviate the problem. Similar traps in the spring, to intercept the foundresses, accomplishes a lot more in the long run. These traps contain a pheromone that attracts the wasps. Put the traps a good distance away from where you hope to have a wasp-free location.
- In many outdoor areas, people will tie a piece of raw meat suspended over a tub of detergent water. The wasps come and gorge themselves, then tumble into the water and drown. Again, this does not mean that you will get them all and no longer be vexed. Also, you may have to deal with other scavengers that will eat old meat.
- If the wasps are going after your bees, this is a good time to put “robbing screens” on the entrances to your hives. They pretty much stop honey bee robbing and they are helpful with wasp problems, too, where the wasp populations are not too high. You can see my idea of a good design at my Bee Briefs on our Entomology website. See Robbing Screen.
Western Yellowjackets (Vespula pensylvanica) like to hang around or nest near apiaries because it's "one-stop shopping," as former UC Davis postdoctoral scholar Erin Wilson, now an assistant professor of entomology at UC Riverside, said at a UC Davis seminar in December 2010.
Yellowjackets prey on honey bees. They raid the hives (killing the adults and brood, and stealing honey) and take the food back to their young.
Yes, it's that time again when beekeepers figuratively "see red" when they see yellow (jackets).