photo of Asian giant hornet

URBANA, Ill – Wasps have an undeserved bad reputation. While some species can be a tad on the aggressive side, they are, as a whole, rather beneficial, says Ken Johnson, University of Illinois Extension horticulture educator. Admittedly they can be intimidating insects, particularly large ones.

Although Asian giant hornets, also called "murder hornets," are not currently in Illinois, large wasps and hornets are often misidentified as the giant hornet, Johnson says. Key size and color markings help differentiate the species of these Illinois wasps: cicada killers, boldfaced hornets, and European hornets.

Asian giant hornets

Asian giant hornets (Vespa mandarinia) are 1.5 to 1.75 inches long and bulky in appearance. They have a yellow to orange head and orange and black stripes on the abdomen. Illinois Extension provides a helpful fact sheet on Asian Giant Hornets.

Cicada Killers

Cicada killers (Sphecius speciosus) are commonly misidentified as murder hornets and active now, Johnson says. Cicada killers can be up to 1.5 inches long and are black with yellow markings on the thorax and abdomen. They have large, rust-colored eyes, as well as orangish-red wings and legs.

Cicada killers are a native wasp species and, as their name implies, hunt cicadas. Females will fly up into tree canopies to capture and paralyze cicadas. She will then deposit them in underground tunnels where she will lay eggs on them. When the eggs hatch, the larva burrow into the cicada and begin to feed on them, while the cicada is still alive. The larva will overwinter in the burrow and pupate in the spring. Adults will begin to emerge in July, around the time when annual cicadas start emerging and will live into September.

"Cicada killers tend to build their burrows in well-drained areas with light-textured, sandy soils that are in full sun," Johnson says. "They can often be found along sidewalks or patio edges, in flower beds, gardens, or lawns."

When building their burrows, cicada killers may bring a lot of soil up to the surface.

While the larvae feed on cicadas, the adults feed on flower nectar and tree sap. The males are territorial and will try to intimidate things, including humans), that enter their territory. Males are harmless, though, and cannot sting, Johnson says. 

Females are not aggressive and typically won’t sting unless handled or stepped on. Because of this, control is often unnecessary, Johnson says. 

One way to discourage nest building in yards is to have a healthy, dense stand of turf. "If they are nesting in landscape beds, mulch or a ground cover can be used," Johnson says. "Another potential strategy to discourage them from nesting in an area is to make sure that the soil remains moist. The wasps don’t like wet soil, and watering the ground may help the soil settle into their tunnels, further discouraging them."

Insecticides containing permethrin and carbaryl used at the entrances of their tunnels can help in management when used as they emerge in July.

Baldfaced hornets

Baldfaced hornets (Dolichovespula maculata) are another native wasp species. They are 0.5 - 0.8 inches in length and have a black body with distinctive white markings on their head. They also have white banding on the last few segments of their abdomen.

Unlike cicada killers, baldfaced hornets are social insects. They build aerial nests at least 3 feet above the ground, attached to tree branches, typically near wooded areas. They can also occasionally be found in shrubs, on utility poles, or the siding of homes, Johnson says. Like other social wasps, they will defend their nests and sting if they feel threatened.

A single queen starts each baldfaced hornet nest. "She will begin constructing the nest by collecting wood fibers and mixing them with her saliva," Johnson says. "This will create a papery material that she will use to create the nest. After she has built a small nest, she will lay eggs."

The workers from these eggs will take over nest construction, foraging for food, and caring for the young while the queen focuses on egg-laying. Near the end of summer, colonies will produce new queens and males. They mate, and the females will overwinter and begin new colonies in the spring.

Baldfaced hornets capture other insects, particularly flies, to feed their young. Adults will also visit flowers to feed on nectar as well as other sugary food sources, such as fruit and tree sap.

European hornets

European hornets (Vespa crabro) were first found in the United States around 1840. These hornets are about 1 inch long with yellow and brown coloration. They have black and yellow-banded abdomens, with the black bands extending into V-shaped markings. One unique thing about European hornets is that they are active at night, unlike other bees and wasps, Johnson says.

"European hornets are also social insects. Their colonies will begin as a single queen, and will grow over the year, and can contain 300 or more workers by late summer. They create nests in cavities, such as hollow trees, and, on occasion, wall voids."

Like baldfaced hornets, they collect wood fibers to build their nests. These hornets will defend their nests and sting if they feel threatened, but they are not as aggressive as some other social wasps, Johnson says. During mid- to late-summer, new queens and males will be produced. They mate and the queens find somewhere to overwinter, such as under loose bark or in tree cavities, until spring.

The adults can occasionally be pests. They may feed on fruit trees in the fall, and they may girdle twigs and branches of trees and shrubs to feed on sap (or to use the fibers to build their nests). Despite this, Johnson says, they are beneficial. "Baldfaced hornets capture a variety of different insects, such as crickets, grasshoppers, large flies, caterpillars, and yellowjackets, to feed to their larva."

Both baldfaced and European hornet colonies are annual and die after a hard freeze; therefore, unless the colonies pose a threat, it is best to leave them be," Johnson says. "If they do pose a threat, a ready-to-use wasp and hornet spray may be used. Since European hornets are attracted to light, make sure to place your light source away from you and wear protective clothing. 

SOURCE: Ken Johnson, Horticulture Educator, University of Illinois Extension

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