Wednesday, June 5, 2013

Where Are All My Friends?

I was very dismayed to hear from my parents that Brood II of Magicicada septendecim, the 17-year periodical cicada, has almost completely bypassed New York City. I've been trying to talk them into catching some for weeks now, and apart from these few my sister saw on a college tour of Bard, they've apparently been scarce:

Just be glad that our campus isn't overrun with these majestic, 2-inch long insects, which were apparently getting stepped on by all the students. I've been following several cicada-tracking websites, hoping to find an emergence that isn't 3 hours away by car. Here is the most recent disappointing image:

As you can see, New York is pretty devoid of interesting bugs, and has been since the last cicada emergence in 1996. Apparently they brood underground and their eggs are laid in old-growth trees that haven't been disturbed, a rarity in a city whose infrastructure changes almost daily.

The two other species of cicada with 17-year life cycles are markedly different: M. septendecula has a smaller body with thinner orange markings, and M. cassini is all black. From what I've learned in EEMB 116, a class you should not take unless you enjoy handling things with lots of legs, these species and several others that emerge every 13 years have synchronized their life cycle to prime numbers to prevent the prediction of their next emergence by predators, of which they have many. Brood II, one of 17 Northeastern populations and one of 12 broods synchronized to a 17-year cycle, is the most NYC-centric; Brood X covers the largest geographic range in the U.S. and Brood IV is known for the densest outbreaks: up to 1,000 individuals per square meter in Kansas!

Louis Sorkin, an entomologist at the Museum of Natural History (where I'm working this summer) bravely answered the questions of many an anxious city slicker:

"The eggs are deposited by the females by slicing into smaller branches with the ovipositor. Eggs require 6 to 10 weeks of incubation. The newly hatched nymphs are smaller than the size of a grain of rice. These fall to the ground. I suppose if you stayed under trees at the time of hatching, you could be pelted by these nymphs. Other than that, their activity will mostly go unnoticed. Emergence of nymphs and progression to mature adults with chorusing and mating continues for a few weeks. The adults have to feed on tree fluids, too. So probably 4 to 6 weeks, but is temperature dependent, so cooler conditions slow things down and warmer conditions speed things up. I'm not sure how long it takes for the shed skins or exuviae to decompose completely, but they are quite resilient. Bodies of dead cicadas also take time to decompose. Foraging ants will probably cut them up to bring back to the nest to feed the larvae. You can use the dead cicada bodies for plant fertilizer."

How practical. Cicadas neither bite nor sting, and belong to the suborder Auchenorrhyncha along with leafhoppers and spittlebugs. As Sorkin said, they feed by tapping into plant xylem, and on rare occasion have been known to mistake a particularly beefy human arm for a branch if they are allowed to remain there for an extended period of time. The long, sharp stylet that they usually use to pierce through bark is said to be quite painful.

Here is an interesting article on the museum's restored cicada display if you're interested in further reading.

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