Sunday, August 12, 2012


What: After returning from a 8 day trip in Alaska, I'm so grateful to return for the crescendo of summer buzzing through the trees and meadows here in Burlington. Last night Callan and I paddled from North Beach to downtown to listen to the Lumineers play a lakefront concert. Old Crow Medicine Show headlined and we could hear them playing in the distance as we headed back home. I think the clicks from the bats, chirps from the angle-wings, croaks from the green frogs, and zzzzzzipsss from the katydids definitely upstaged them.

Ecological notes: Most of these insects are hard to spot because they're making their noises from high up in the canopy or once you get close they go silent. Occasionally I spot one of the musicians on the ground. Today while walking to the farmer's market I was lucky enough to find a pair dog-day cicadas (Tibicen sp., perhaps T. canicularis) locked together in their nuptial celebration. Lamely, I'm not sure but I think the one on the left is the female.

I took the below photo on May 11th this spring, in which you can see the smaller male copulating with the female - this is a derived behavior, as a primitive characteristic is to have the female on top. Not surprisingly, it's both intriguing and somewhat repulsive at the same time; I can't quite seem to figure out why some insects mate in this position while others like the cicada lock in a position facing away from one another - if anyone knows, please post a comment. I don't claim to be an expert on insect sex (see Dr. Tatiana's Sex Advice to All Creation for that), but from what I can gather the male has a telescoping "penis" composed of an aedaegus, a structure that extends from the abdomen - the rear third of an insect - and an endophallus, which extends further to deposit spermatophores into the female reproductive tract. Insects don't have swimming sperm, but encapsulated spermatophores and so need to be directly deposited to the site of implantation.

Aptly named, the dog-day cicadas are among the later insects to start making their buzzy wing-flapping noises. The related periodic cicada (Magicicada sp.) has a life cycle that results in outbreaks over large geographic areas every 13 or 17 years, depending on species. Both numbers are prime numbers and probably prevent repeated overlap with any would-be predators that might be on 2,3, 4, or 5 year population cycles (a predator with boom populations every 5 years would only over lap with the periodic cicadas every 85 years). Dog-day cicadas appear every year (and are therefore also known as annual cicadas). Not coincidentally, annual cicadas are predated upon by cicada killer wasps, while periodic cicadas are not known to be predated upon by any wasps. To hear a sampling of Tibicen cicadas check out Insect Singers

Where: My backyard and all over Burlington. The image was taken on Latham Ct in the middle of the road and I found a couple of dead ones nearby.

Etymology notes: Dog days refers to when Sirius, the Dog Star is overhead in the sky, which occurs during late summer.

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