ENHS Nature Trails Jan. 98 Article 3

Yellow jackets, an endangered species?
by Melody Clarkson

In some areas of central Japan this seems to be true. And with the decline of the species, the price goes up for a favorite relish, samurai, or yellow jacket larvae seasoned with soy sauce or sake and mixed with boiled rice. Here in the Willamette Valley last summer, we would gladly have shared all our yellow jacket larvae with those whose appetites include these vespids. Vespids are eusocial insects whose members cooperate within their own family, commonly known as wasps, hornets, and-our marauders of summer picnics-yellow jackets. So we've had it all wrong when we continually swatted away at the ornery vespids and prepared separate little plates for them to distract them from our main course; they should have been our main course! Peoples of southeast Asia as well as indigenous peoples of both North and South America have enjoyed the protein of vespids for centuries. Nests with queen and workers intact are often collected early in the summer and then farmed for the larvae through November.

Even though most of us won't be changing our diets to include yellow jackets, they do fill a niche in the environment. In the Willamette Valley, yellow jackets fall into two categories: the predators and the scavengers. They are difficult for the casual observer to distinguish visually, but most likely the predatory varieties are off eliminating unwanted forest pests, and the scavenger varieties are foraging in our backyards for protein and sweets--and when foraging, SHE doesn't hesitate to sting. Only the female stings, as the ovipositor doubles as the stinger. Few female yellow jackets are destined to lay eggs, but all females use their ovipositor to sting. Males are much more plentiful later in the summer as the nests grow in size and the infertile eggs develop into the male yellow jackets. But, who asks gender when dodging from the pest?

Not unlike humans, growth of the colony seems to be the motivating factor for the yellow jackets' existence. And not only growth for their colony, but only their colony of like brothers and sisters. Even the scavenger species can become predatory and take over the nest of another yellow jacket family early in the season to increase the strength of the colony. The usurpers often put into slavery the conquered workers, forcing them to feed the conquerors grubs. While feeding the larvae, the adult yellow jackets often practice a form of trophallaxis: The adult exchanges the masticated insects or other food for the pleasure of milking a sweet substance from the legless larvae, enervating the larvae in the process. Researchers suspect that this practice may keep the female population so malnourished that they can become only workers. A few special large cells are designed in the nest for future queens, who possibly even get a different diet.

When foraging, yellow jackets like to feed on the nectar of flowers; on the honeydew secreted by leafhoppers, mealybugs and scale insects; on insect larvae; and on the corpses of dead mammals, fish, and flies; they will tackle flies both dead and alive. (Researchers have counted yellow jackets' eliminating flies at the rate of 227 per hour.) Once the yellow jackets find a lucrative food source, they tenaciously and voraciously return to it until it offers no more sustenance--thus, they don't get the message when we constantly swat and swear them away from our hamburgers.

Yellow jackets generally build their nests close to their food sources: never more than 400 meters from a protein source nor one kilometer from a honey source. In their territory they pollinate our flowers; help keep leaves free of honeydew which can encourage fungi and ants; eat the insect larvae of harmful insects; keep rotting corpses, however small, cleaned up; and possibly even discourage field mice from living nearby. (In Britain studies have shown that field mice will not take up residency near yellow jacket nests.) These nests can grow to include over 10,000 cells and 5,000 live workers by late summer when the yellow jackets will bring in 3,000 to 4,000 prey a day. Who could destroy in one nighttime swoop these diligent vespids? We should all use the adage, "If it's not threatening you and yours, leave it alone." Besides, the nest size declines and the worker population dies off completely as cold weather arrives. The few mated females left overwinter in forest debris or nest debris and begin their own families in the spring, beginning anew the physical building of cells in usurped tunnels or in their own excavated tunnels.

Before you make the decision to put a bowl over the nest at night (a benign method of eradication--it works if there is only one exit), think not only about the yellow jackets' benefits to your garden, but also about the euphoria you will be eliminating from the life of a future queen: When she emerges from her nest in the fall, she often has 100 suitors waiting for her.

Unfortunately, 15 to 20 deaths occur every year in the United States due to yellow jacket stings. Severely allergic Individuals suffer anaphylactic shock from the serotonin (a vasoconstrictor) injected via the ovipositor. Allergic individuals need to carry adrenaline (epinephrine) syringe kits anytime they are in yellow jacket territory. The solitary wasps or hornets do not pose the same threat as the eusocial yellow jackets and cause little more than minimal pain when they sting.

An aside: Sugare, jibachi and hebo are names for Japanese entrees using the delectable wasp.

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