Annual Dog-Day Cicadas (Tibicen spp.; family Cicadidae) are starting to sing in southern Ohio. This means their nemesis, Cicada Killer Wasps (Sphecius speciosus), will soon be seen cruising woodlands and landscapes in search of their exclusive prey.
The annual cicadas share several behavioral traits with periodical cicadas (Magicicada spp.; family Cicadidae). The nymphs of both types of cicadas develop underground sustained by juices sucked from tree roots and it takes multiple years for them to complete their development from eggs to new adults.
Periodical cicadas are so-named because it takes 17 or 13 years for new adults to emerge en masse in spring. It takes 2-3 years for dog-day cicada nymphs to complete their development; however, some adults emerge every year due to overlapping generations. The adults appear sporadically throughout the “dog days” of summer usually beginning in July.
Like their periodical familial cousins, dog-day cicada males also "sing" to attract females. However, they do not "chorus" with large numbers synchronizing their song. An occasional dog-day cicada buzzing to entice a female doesn't compare to the cacophony created by a multitude of periodical cicadas. It's like comparing a barbershop quartet to a million man chorus!
As with periodical cicadas, dog-day cicada females use their long, spade-like ovipositors to insert eggs through the bark of twigs and into the white wood. The resulting damage splits the bark and white wood leaving deep longitudinal furrows of ruptured tissue. The injury often causes the twig to die, the leaves to turn brown ("flag"), and the twig to detach and drop. However, owing to the smaller numbers of dog-day cicadas, their egg-laying damage usually goes unnoticed.
Dog-Day Cicada Nemesis
Cicada killer wasps feed exclusively on annual dog-day cicadas; they do not prey upon periodical cicadas. That's why the wasps appear on the scene long after a periodical cicada brood emergence has left the scene. The synchrony with annual cicadas makes sense if you consider that the wasps would starve to death waiting 13 or 17 years for a cicada meal.
The wasps measure 1 1/8 to 1 5/8" in length and are one of the largest wasps found in Ohio. As with all Hymenoptera (wasps, bees, etc.), only the females possess stingers (ovipositors); however, they are not aggressive. The males are aggressive, but they lack stingers.
The females spend their time digging and provisioning burrows with paralyzed cicada-prey. They prefer to dig their brood burrows in bare, well-drained soil that is exposed to full sunlight. Although the wasps are considered solitary, all of the females have the same nesting requirements. So it is not unusual for there to be numerous burrows, and wasps, in relatively small areas.
The males spend their time establishing and defending territories that encompass multiple females. They are notoriously defensive and will aggressively buzz any transgressor who dares to enter their territory including other males as well as picnickers, golfers, volleyball enthusiasts, and gardeners. Fortunately, it's all a rouse since they lack the necessary equipment to deliver a sting.
Cicada killers are considered beneficial insects. However, their large size coupled with low-level flights over sand volleyball courts, sparse lawns, and bare areas in landscapes can be disconcerting generating demands for control options.
Insecticide applications to kill the killers is not recommended. First, they are beneficial insects. Second, the females are not aggressive; stinging encounters are very rare. Finally, the best way to manage cicada killers is to modify their habitat. Renovating lawns late this summer to thicken the turfgrass will keep the killers out of lawns. Applying mulch to cover bare soil or raking mulch to disturb and redistribute possible burrowing sites will convince females to nest elsewhere. The same is true for golf course sand traps and sand volleyball courts: periodical raking will prevent the wasps from becoming established.
A Word about Big Wasps
The annual appearance of our native cicada killer wasps invariably triggers e-mails and phone calls to Extensioneers in Ohio and elsewhere about Asian Giant Hornets (Vespa mandarinia) or the subspecies, Japanese Giant Hornets (V. m. japonica). To be clear: these non-native hornets have never been confirmed in Ohio or elsewhere in North America.
Unfortunately, some online postings of Asian hornets "found" in the U.S. show images of European Hornets (V. crabro), which are rare but can be found in the U.S. including Ohio, or cicada killer wasps. This is not to say the Asian giants won't appear in the U.S., but please get a confirmation from an official agency (e.g. ODA, USDA APHIS, etc.) before adding to the web confusion.