After emerging from her gallery, this female cicada killer prepares to hunt her next victim.
Beneath my zinnias in the front flower bed a female cicada killer has prepared her subterranean gallery.
Last week we met male cicada killers in my front flower bed as they battled for space and the right to mate with female cicada killers once they finally make their appearance. Well, the ladies are now in town, and they are putting a beat-down on the boy band of hapless male annual cicadas singing their hearts out in the treetops. Unlike their periodical cousins who make an appearance once every thirteen or seventeen years, dog day cicadas join us every summer. The female cicada killer uses several species of annual cicadas as a source of food for her babes. The life cycle of the female cicada killer wasp is closely synchronized with that of her prey. After spending most of her time underground as a larva and then as a pupa, she completes her development in summer and emerges in July coincident with the appearance of annual cicadas. After emerging and having a brief romantic interlude with the victor, I suppose, of the territorial war games, the female cicada killer constructs a gallery in the ground, Which will serve as the chamber for her developing brood. This chamber consists of a tunnel with individual brood cells or nests.
After excavating her subterranean brood gallery, the female cicada killer hurries off to hunt and soon returns with a paralyzed cicada to serve as food for offspring.
When the nest chamber is complete, the female cicada killer searches branches for the boisterous annual cicadas. Upon finding a suitable victim she grapples with the cicada and stings it. Her remarkable venom does not kill the cicada. It only paralyzes the cicada, rendering it unable to fly or otherwise defend itself. The cicada killer then straddles the cicada, which may far exceed her weight, power-lifts the victim into the air, and then flies it back to the burrow. Both amateur and professional insect enthusiasts have reported instances where cicada killers straddling a cicada have climbed vertical structures, such as tree trunks, in preparation for takeoff. Apparently, a height advantage is necessary to attain flight while transporting their massive load. Once the heavy lifting is over and the female arrives back at the nest, she quickly wrestles the cicada into the brood chamber.
For this female cicada killer, sandy soil in my backyard was a fine place to build a gallery but locating the gallery amongst a sea of grass appears challenging on the return trip, especially when transporting a cicada more massive than itself.
Paralyzed cicadas are sometimes abandoned near the entrance to a nest.
In a fascinating display of gender selection, the female cicada killer chooses the sex of her spawn. If a male wasp is to be born, the female lays an unfertilized egg on the paralyzed cicada. If the cicada-killer decides to produce a daughter, she will return to the treetops, collect one or two more cicadas, place them in a nest chamber and then lay a fertilized egg on one of the victims. The fertilized egg will hatch into a ravenous daughter capable of consuming all of the cicadas and developing into a female wasp. The explanation for this fantastic behavior is in part due to the fact that female cicada killers are about twice the size of males; hence, female larvae need twice as much food to complete their development. Two cicadas for the ladies and one for the gents. After depositing the egg, the cicada killer seals the nest, excavates a new brood nest and resumes her search for cicadas.
Back in the nest chamber, the egg hatches and the developing larva attaches itself to the skin of the paralyzed cicada and literally eats it alive - trapped in an underground tomb and paralyzed while being eaten alive, indeed a sad end for the dog-day cicada. After a few weeks, the cicada killer larva completes development and forms a case in which to pupate underground. It spends the remainder of the summer, autumn, winter, and spring in the chamber before emerging as an adult the following year to resume the hunt for cicadas.
The magnificent stinger of the female cicada killer will deliver a paralyzing but not lethal sting to her victim.
As discussed in the last episode, while cicada killers look ferocious, they do not attack humans and stings are very rare. The only report I have heard of a cicada killer sting came when someone inadvertently kneeled on a female while working in the garden. I photographed cicada killers at very close range, inches, without any problems. A curious female approached to ogle me when I put my nose in her gallery, but no harm came of this. Homeowners may be dismayed when cicada killers construct large numbers of nests in their lawns. I find their presence in my landscape delightful because these guys and gals are so entertaining, but not everyone feels the same. Attempts to control cicada killers with pesticides may be futile. While you can kill the current batch of cicada killers in your lawn in the short term, it is the texture, exposure, and drainage of your soil that attracts a new crop of cicada killers to your lawn each year. Improving the density of your turf may help by reducing the amount of exposed soil that could attract females seeking nest sites. The real cicada killer expert, Professor Chuck Holliday of Lafayette University, recommends keeping the soil at the nesting sites unusually wet, as nesting females are attracted to well drained soils.
Acknowledgements
Information about cicada killers came from Chuck Holliday’s magnificent cicada killer website. For more information about cicada killers, including videos of them in action, please visit his website at: http://web.archive.org/web/20141022032916/http://sites.lafayette.edu/hollidac/research/biology-of-cicada-killer-wasps/