Adult annual cicadas, including the pictured Dog-day Cicadas, have emerged from their subterranean dwellings. High up in trees most males are vibrating their abdominal tymbals (drum-like organs) in order to woo female cicadas with their “song.” Thanks to an abdomen that is relatively hollow, the sound is intensified, and very audible to human ears as a high-pitched whining drone, somewhat resembling a buzz saw. We associate it with the hot, humid “dog days” of July and August.
Annual cicadas emerge from the ground (where they have been feeding off of the sap of trees through the trees’ roots for two to four years) every year as nymphs. They climb a tree, split and emerge from their exoskeleton, or outer skin, and pump their wings full of fluid. After their exoskeleton dries, the adult cicadas (also called imagoes) head for the canopy, and males commence “singing” to attract a mate. Within two weeks mating takes place, eggs are laid in slits of live branches and the adults die. After hatching, the nymphs will drop to the ground and burrow into it with their shovel-like front legs. (Thanks to Wallie Hammer for taking and providing today’s photograph. Mating usually takes place in the canopy, and therefore rarely seen.)
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Periodical Cicada Brood II has gotten a lot of press this summer, as this brood of 13 and 17-year cicadas is emerging from Connecticut south to Virginia. These species are referred to as “periodical” cicadas because they are developmentally synchronized and appear in large numbers every 13 or 17 years. There are also “annual” cicadas – cicadas that appear every summer. They may spend several years as immature insects under the ground, feeding off the sap in roots, but some of them mature and appear every summer. Northern New Englanders are familiar with different species of annual cicadas, including Okanagana rimosa, which usually emerges in mid-summer and fills the air with its courtship call on hot, humid days. The emergence of cicadas is triggered by the temperature of the soil they are in — once the soil 8 inches below the surface gets to 64 degrees Fahrenheit, annual cicadas are on the move. (Thanks to Holly Lanigan for Periodical Cicada photo op.)