From Wisconsin DATCP
Every August and September, it seems to be yellowjacket season in Wisconsin. During this time, it is normal to see social wasps like yellowjackets, paper wasps, and bald-faced hornets. These insects build up their numbers throughout summer, and one nest can have as many as 4,000 individuals. Yellowjackets live until fall, when only the queen overwinters to form a new colony the following year. During summer, yellowjackets feed on larvae, but once the queen leaves, food becomes scarce and that is when they may become aggressive with humans. The best advice for avoiding stings is to minimize putting sugary drinks, fruit, pet food, bird feeders, or other attractive substances outdoors near where you spend time in the yard.
Despite the bald-faced hornet’s name, it is also a type of predatory social wasp, like the yellowjacket. However, unlike the yellowjacket, it is white and black, rather than yellow and black, and it can be more aggressive towards humans.
 Many social wasps defend their nests by stinging intruders. However, after a few hard frosts, social wasp colonies die each fall. A few weeks of fall-like weather should be enough to control these colonies. |
Picture (above): Bald-faced hornet; David Cappaert, Bugwood.org
 The giant cicada killer wasp and the great golden digger wasp are two solitary wasps that are common in Wisconsin, and they are also native to Wisconsin. |
Picture (above): Giant cicada killer; Russ Ottens, University of Georgia, Bugwood.org
 The giant cicada killer wasp and the great golden digger wasp have more in common than lengthy common names. They both nest in the ground, are not aggressive towards humans, are beneficial insects, and have been confused with invasive hornets, like the large Northern Giant Hornet detected in Washington state in recent years. |
Picture (above): Great golden digger wasp; David Cappaert, Bugwood.org
Recently, near Savannah, Georgia, a new invasive hornet named the yellow-legged hornet (YLH) was detected in the U.S. for the first time. Two colonies (and their nests) have been detected and eradicated so far. If established, this invasive, non-native pest could become a major threat to honey bees and native pollinators. More information about YLH is available from the Georgia Department of Agriculture and the U.S. Department of Agriculture (USDA).
While it is important to know how to tell the difference between native bees and wasps and emerging pests, we encourage you to report suspected invasive hornet finds to your state apiarist.
Find more information in the UMN Wasps and Bees webpage.
See these UW-Madison visual ID guides:
