Saturday, August 05, 2006

Cicadas and Cicada Killers

Cicada-killer Wasp [wings open]

Cicada-killer Wasp [wings closed]
Photos by Lloyd Spitalnik [
taken at Sterling Forest - 8/1/06

This year's first annual or dog-day cicadas showed up in Central Park about two and a half weeks ago. Jimmy Lewis, one of the regular Moth devotees, heard a single Cicada song on the afternoon of July 19. About a week later we began to see cicadas emerging from their larval cases on the usual trees near Cedar Hill, at the path to Fifth Avenue and 79th Street. [See post of 7/31/06]

If the cicadas are here, can the cicada-killers be far beyond? One follows the other, as the night the day. [That may have a familiar sound, but Shelley and Shakespeare's copyrights expired a few years ago.]

Three nights ago Nick, Noreen, Lee, Jimmy and I made our way to the usual Cedar Hill spot, near a small outcropping where we've watched cicada-killer wasps digging their tunnels in years past. Sure enough, we saw the tell-tale little mounds of damp earth near the rocks, with small tunnel-like holes at the end of each mound. Within a minute or two, out came a cicada-killer, the largesat wasp in North America. She [only the female makes and provisions the nest] was backing out of the tunnel, adding another little pile of earth to the mound. Then back she went to dig some more.

Below, some internet information about cicadas and some rather gruesomefacts about cicada-killer wasps.


from Wikipedia]

Most of the North American species of cicada are in the genus Tibicen—the annual or dog-day cicadas (named after the "Dog Days" because they emerge in late July and August). [Our Central Park cicadas are annualacicadas.]

Adult cicadas, sometimes called imagines, are usually between 2 and 5 cm (1 to 2 inches) long. Cicadas have prominent eyes set wide apart on the sides of the head, short antennae protruding between or in front of the eyes, and membranous front wings. Desert cicadas are also one of the few insects known to cool themselves by sweating, while many other cicadas can raise their body temperatures voluntarily to around 40°C, even when the air temperature is only 18°C.

Male cicadas (and only males) have loud noisemakers called "tymbals" on the sides of the abdominal base. Their "singing" is not stridulation as in many other familiar sound-producing insects like crickets (where two structures are rubbed against one another): the tymbals are regions of the exoskeleton that are modified to form a complex membrane with thin, membranous portions and thickened "ribs". They rapidly vibrate these membranes with strong muscles, and enlarged chambers derived from the tracheae make their body serve as a resonance chamber, greatly amplifying the sound. Some cicadas produce sounds louder than 106 dB (SPL), among the loudest of all insect-produced sounds. (This amazing sound has frequently inspired haiku poets in Japan to write about them.) They modulate their noise by wiggling their abdomens toward and away from the tree that they are on.

Only males produce the cicadas' distinctive sound. Both sexes, however, have tympana, which are membranous structures used to detect sounds; thus, the cicadas' equivalent of ears.

Cicada killer Wasps

The cicada killer wasp, Specius speciosus is the largest wasp we have in the Eastern United States

Cicada killers, which range from 1" to 1.5" and have a wing span of nearly 3", are solitary digger wasps that do not make paper nests or hives like many of their relatives.

A female cicada killer constructs a nest in the ground consisting of long tunnels. Dry, sandy or slightly elevated soil is preferred because it does not invite mold or mildew.

The burrow has a gentle sloping entrance about six inches long then usually a right angle turn. The turn is probably for protection against other predators. The tunnel then continues another 6 to 8 inches and ends in one or several globular cells about 1.5" in diameter. Once the nest building is completed, the hunt begins.

Adult wasps emerge at the same time as when the cicada are most numerous. Often you can see the large cicada killer flying around a tree in which a cicada is singing. Suddenly the regular buzz of the cicada breaks into a distressed cry (similar to an electric shaver when you try to cut steel wool). The cicada, which has no defense except flight, is quickly overcome by the wasp's sting, and often both fall to the ground during the struggle. The sting does not usually kill the cicada, but paralyzes it and throws it into a comatose condition from which it never recovers.

Now the real work begins. The cicada, being larger and heavier than the wasp, cannot be flown away simply. It has to be laboriously dragged up a tree or other higher point. Frequently it takes the cicada killer an hour or two to get high enough to fly and glide at a downward angle toward its nest.

At long distances from the burrow, several climbs have to be made and the return trip may take the better part of the day. After reaching the burrow, the cicada is dragged down into one of the cells and a single egg is deposited near the base of the cicada's middle leg.

The egg hatches in 2 to 3 days and the larva immediately starts to feed on the paralyzed victim. If the cicada dies, the venom of the wasp's sting helps to preserve the tissues for the feeding larva. The larva feed from the outside until full-sized in about a week or so. Only the hollow shell of the cicada is left over. Often two cicadas are placed in one cell with on egg. This results in a larger adult wasp. It is believed that wasps resulting from one cicada turn into males, while those resulting from two cicadas turn into females. Females are always much larger than male.

After the larva reaches its maximum size obtainable from the food supply at hand, it spins a silken cocoon which is completed in two days. This "silken" cocoon is a mixture of earth and silk, and has special breathing holes around the middle. The larva remains unchanged and stays in this "resting" stage throughout the winter.

In the spring, the larva changes into the transitional pupa, shortly before the appearance of the adult. The newly emerged adult chews its way out of the cocoon and digs its way to the surface and completes its one-year life cycle. Like all wasps, the cicada killer can sting as many times as it cares to. Being our largest wasp, the sting is severe, and needless to say, should be avoided.