Making themselves at home
WORTHINGTON — Students and parents may be turning their thoughts to fall as the first day of school nears, but for bugs, summer is still in full swing — and they are out and about enjoying the weather.
Many Worthington residents have noticed cicada killers — wasps that are large insects resembling hornets — taking up residence this year in their lawns and flower beds. The bugs may look intimidating, but unless directly threatened, their appearance is mostly for show, and they rarely will harm people.
“The past couple years, we’ve been seeing more of them,” said Chrystal Dunker, Prairie Ecology Bus Center (PEBC) executive director.
The PEBC has an insect theme this year, and Dunker said many people have been commenting on the cicada killers as they walk through the exhibit.
“Even around my own house, I’ve seen them," she added. “They have a good food source, so it stands to reason we’d see more of them.”
Cicada killers, a type of solitary wasp, construct their individual nests in the ground, primarily in sandy soil.
“But they are gregarious with many nests in a small area,” said Jeff Hahn, University of Minnesota Extension entomologist. “When you see them fly, it looks like a colony, but it’s really a bunch of individuals going about their business.”
As the name suggests, female cicada killers hunt and attack cicadas using their stinger to paralyze the cicada. The female then brings the cicada back to her burrow and lays an egg on the cicada. The cell is closed with dirt and, once the egg hatches, the larva uses the cicada for food.
Cicada killers are up to 2 inches long and identified by their smoky colored wings. They are mostly black with yellow in their abdomen. Their legs are reddish-brown, and they may also have reddish brown on the middle of their thorax.
Because of their size, cicada killers can often be heard and make a sound similar to a hummingbird — although they are easiest to identify when carrying a cicada.
Despite their size and similarity to yellow jackets and wasps, cicada killers are rarely dangerous to people unless directly antagonized.
“We have the females that are capable of stinging, but they are uninterested in people,” Hahn explained. “If you block their way, they will go around and do what it takes to avoid you. The risk of them is negligible.”
Males, on the other hand, have no stinger, and yet will aggressively chase away other males or people that are threatening their nests.
“So you have something that can sting, but never does and something that acts aggressive but can’t do anything,” Hahn said.
Hahn added that July, August and September are common months to encounter cicada killers.
Great golden digger wasps are also common in the area, and — as their name implies — also dig their nests in the ground.
Similar to cicada killers, great golden digger wasps rarely pose a threat to humans. With large amber wings, a black thorax and amber-brown legs, the wasps often build their homes in sunny areas with compacted clay and sand, such as flower beds or gardens.
Because cicada killers and great golden digger wasps have individual burrows, getting rid of them can be a laborious process.
“You would need to treat each burrow separately with an insecticide,” Hahn said. “A liquid isn’t very effective. You would need a dust.”
He added, however, that the insects will likely go away on their own, and are unlikely to return to the same site in future years.
Dunker agreed with Hahn and said that unless there are nests near homes or other frequently used outdoor areas, she recommends leaving them alone.
“They are beneficial and aren’t hurting anything,” she said. “If people aren’t fearful, a great thing to do is keep an eye out and watch them. It’s interesting to see them excavate and see the cicada killers take a cicada down in the tunnel.”
Cicada killers are very conspicuous insects and are hard to miss because of their size, yet Hahn emphasized that they pose little danger to humans.
“There have been a variety of times when I have stood amongst them, and they have never bothered me,” Hahn said. “I would emphasize for people to be patient with them and make sure you correctly identify them. It would be a bad mistake to confuse them with other wasps or hornets.”
Hahn added that cicada killers may be confused with yellow jackets, which are much more aggressive and dangerous to people. While yellow jackets often build their nests on buildings or trees, they can also build nests in the ground.
“They will sting repeatedly and will protect their nest if they think it is under attack,” Hahn said. “If you see a number going into the same hole, it’s a yellow jacket.”
Daily Globe Reporter Alyson Buschena may be reached at 376-7322.