To coincide with the annual emergence of cicadas, the cicada killer wasps are also back in action. Cicada killers, as their name implies are predators of cicadas. Last night, I noticed a wasp flying low to the ground as the sun set. This wasp recently emerged from a burrow, provisioned with cicadas by its mother last summer. If you have not yet seen one, just wait – There will be more!
The first thing you may notice about the cicada killer is its sheer size. The second may be its acrobatic speed. Next, you may wonder if this big, bold wasp is dangerous. Here’s the thing: Cicada killer wasps may look scary, but they rarely sting people.
The most common complaint from homeowners is the damage to yards, landscapes, sand pits, and gardens caused by the burrowing nature of cicada killers, rather than any human health hazard. Cicada killer wasps are considered nuisance pests because nesting locations are often adjacent to homes and their presence elicits fear. The female cicada killer is capable of delivering a painful sting if handled, trapped in clothing, or stepped on without shoes, otherwise she is not a threat to people. Likewise, the male wasp lacks a stinger, and so, although it appears to be aggressive in nature, it is harmless.
Of the solitary wasps, the cicada killer is the largest species in Nebraska, reaching lengths of 1¼ to 1¾ inches. They have large, rust-colored eyes, wings, and legs. Their abdomen appears hairless, black and marked with bright, bold yellow patterns (usually three broken bands). They are considered solitary because they do not have a central nest with many workers. Instead, cicada killer wasps push out a lot of soil as they excavate burrows in the ground. In favorable locations, nesting aggregations tend to form where it’s not uncommon to see over 25 or more cicada killer burrows within in a small area.
Biology and Behavior
Female cicada killers possess a large, visible stinger, which is a modified egg-laying device. She uses her stinger to paralyze cicadas one at a time. Once she subdues her prey, she flies back to the nest, drags it into the entrance hole, down into the burrow. When she has collected enough food, she lays an egg, and begins another cell, continually returning to the surface to hunt and capture more cicadas. The larval wasp, which looks like a legless white grub, emerges from the egg a few days later and feeds on the living cicada. Pupation occurs in spring and adults emerge in late June or July. There is one generation per year.
The male cicada killers are smaller than females and remain close to the nesting location. Males do not dig nests or catch prey. Males patrol the area, flying fast and erratically in attempt to chase off any creatures (including humans) from the nesting site.
Damage to Landscape
Cicada killer wasps become a pest midsummer when cicadas are active. They dig burrows in well-drained, light-textured soil in areas of full sunlight. They prefer areas with sparse vegetation, but will move mulch out of the way. This would include edges along lawns, sidewalks, driveways, golf course sand pits, and garden beds. They also burrow in spaces between landscape features such as retaining walls, garden planters, under porches, and post holes. Sometimes they will even burrow in the middle of the turf. Burrows are often identified by a half-inch diameter hole with a distinct U-shaped mound of kicked out soil. Without a wasp sighting, homeowners may mistake the holes for rodent damage.
Cicada killers are considered beneficial insects and disappear when the cicadas die off in the fall. There is no permanent damage or no harm to plants and landscapes. Homeowners may attempt to modify the environment to discourage burrow excavation such as keeping these favored nesting sites excessively wet. Other things that may change the environment enough that they may nest elsewhere would be to create shade, alter soil type, or increase undesirable mulch in garden beds.
If numerous nests become a problem in the landscape, the infested area can be treated with an insecticide labeled for use on ground-nesting wasps or turf applications. Treating for cicada killers may be time consuming as it takes great effort to find and treat each nest. A direct application of insecticidal dust to each individual hole may be effective as female wasps will contact the toxicant as it enters and exits the burrow (leave hole open). It may be necessary to repeat these efforts as female wasps may also push treated soil away. Be sure to read the pesticide label and follow any safety precautions to protect people, pollinators, and pets.
After the mating and nesting frenzy during the summer, cicada killers may be seen feeding on plant nectar. These wasps die before winter, leaving offspring to develop underground to rise and repeat the following year.
All photos and video taken by Jody Green.
[It is not the Asian giant hornet].