August 28, 2013 | 2
Now that the literal, and metaphorical noise surrounding the emergence of the Brood II periodical cicadas has died down, there is arguably a more interesting invader in town. Spechius Speciosus or the Eastern cicada killer wasp. Cicada Killers live, breath and breed to consume annual cicadas of the genus Tibicen, which who also emerge during July and August. Impressive in stature, personality, work ethic and habits, cicada killers are now out in force.
Up to two inches long and with a robust, glossy black and yellow thorax, cicada killers are large and intimidating. When they first arrived in our yard we were somewhat nervous, but quickly realized that in spite of swarming around us, they meant no harm. The females do have a stinger but you have to be very unlucky, or excessively provocative, to be stung by one. Males have a false stinger used for mating so their habit of dive bombing is for show!
The females are attracted to warm, dry sandy soils. Here they can easily burrow, an activity in which they engage with ferocious energy. A single female will burrow 10-20” deep with up to ten separate chambers for her eggs. She will move several times her weight in soil during the process. She uses her powerful jaws to dislodge the soil and her legs to push the earth. Her legs have special spines to assist in this effort which the picture shows under a digital microscope. She pushes the earth to seal up a previous egg chamber or ejects it on to the mound outside the burrow. In spite of this Herculean effort, some females do share burrows although they will maintain separate chambers for their eggs. The burrows are easily recognizable by the mound of earth outside with a characteristic trench running through it to the hole. Since females are attracted to existing mounds, if you have one cicada killer wasp, you will likely have dozens of them so look for multiple holes and mounds.
Once the female has dug a chamber, she’s off to hunt for cicadas. She paralyzes the cicada with her stinger and then grasps it under her body for the journey back to the burrow; and what a journey it is. Since the cicada is often larger than she is, she suspends it beneath her body, hauls it up a tree and attempts to fly by launching herself off the tree towards the burrow – not once, but repeatedly until she arrives. She repeats this effort for each chamber with female eggs receiving at least two cicadas each. This involves a massive effort and she looks like a jumbo jet flying under a space shuttle. To give an example of the amount of work involved, a female three female eggs and two male eggs will dig five chambers and fly in, or more accurately, glide in no less than eight cicadas. Two for the girls and one for each boy, which explains why females are significantly bigger than males. Exhausting work especially coming on top of her digging!
Once the cicada is safely inside the chamber, the female usually deposits an egg behind a foreleg of the incapacitated, but still alive cicada. This is typically near the hole she created with her stinger so the larva has a ready entrance for dinner. It also a safe haven for the egg from any involuntary spasms by the cicada. She then seals the chamber with dirt from the next chamber and continues the routine. Part of this routine involves familiarizing herself with the location. She will walk several times, back and forth, across the mound before flying around it. Once her chambers are full and her eggs all laid, her job – and life – are done. The exhausted wasp dies.
Meanwhile, after a few days, a wasp larva hatches from the egg and begins to feast on the cicada. Over approximately two weeks, the larva eats the entire cicada except the shell. It then prepares to hibernate for winter by spinning a coccoon. In the Spring, the next stage of its metamorphosis occurs when it leaves its cocoon and becomes a pupa before hatching into an adult wasp.
So much for the girls….but what of the males? The males are entirely focused on mating. They prefer virgins and will compete vigorously within a defined territory typically of less than a yard. As a result, at this time of year, cicadas killers perform a silent swarm around the burrows. The males, who have the curious habit of vomiting on their own heads to keep cool, vigorously dip and dive to find a female, to ward off other males and to investigate anything else that moves in the vicinity including Humans. As mentioned earlier, this can be intimidating at first, but it is a harmless, albeit misguided, part of their search for a mate.
Females appears to judge a male by a combination of his weight and strength, an opportunity she has to judge as the males struggle to compete for a ride. A male will mount the female’s back before mating and engage in what amounts to foreplay. He shakes her head back and forth with his front legs and taps her antenna with his own. It appears that his antenna secretes a sex pherome that arouses the female. Active copulation averages approximately 20 seconds after which the couple spend an hour or so resting together, conjoined, possibly to ensure that no other male interferes until the female is fully fertilized. Once mated, the female works to ward off other potential suitors and the cycle continues.
It has to be confessed that while useful in controlling the cicada population, cicada killers can be a bit of a nuisance in your yard, if only due to the overwhelming numbers. We have had two infestations, one on our back patio between the paving stones which made guests understandably, uneasy. In our last house we had thousands of them on our driveway and therein lies the problem. Left alone, they multiply quickly. There is no cast iron solution to getting rid of them. A ping pong bat or tennis racket is often the first resort, but we have found that constant flooding with a hose pipe to be most efficacious combined with stopping up the burrows. That said, they are beautiful creatures and a welcome relief from the buzz around their periodical cousins.