At a recent potluck, a group of us sat at a picnic table trying to make ourselves heard above the high-pitched buzzing coming from the surrounding trees. The conversation turned to which insects might be responsible for the racket. Were they cicadas? Katydids? Crickets? In the absence of a body to view we were left trying to solve the mystery from other clues.
It turns out, this is a common point of confusion since all our suspects share certain characteristics. Their life cycles are similar, maturing through incomplete metamorphosis; eggs lie dormant in the winter emerging in spring, and develop as nymphs into adults. Adults reproduce in late summer and die off with the cold weather. All three create loud songs as part of their mating behavior.
A cricket produces sound by rubbing a plectrum on one wing against a large vein covered with teeth running along the bottom of the other wing. It positions its wings up and open, to create a resonating chamber. Cricket song is pure, that is, it consists of a single low frequency considered pleasing to the human ear. While their song may be heard in late summer, our local crickets are ground dwellers so they would not have been calling from the trees.
Both cicadas and katydids live in trees. There are at least 65 species of cicadas in California. Male cicadas produce sound by expanding and contracting a membrane, amplified within the large, mostly hollow sound box of the abdomen. The clicks are produced so quickly they blur into a buzzing sound. The volume can reach 100 decibels, about the same as a lawn mower or motorcycle.
Katydids are larger, green insects well-designed to conceal in leaves. They got their name from their call of 'katy-did, katy-didn't'. Like crickets, katydids produce sound by rubbing a wing file on one wing against a comb-like scraper on the other wing. Katydid song has been recorded at 110 decibels, comparable to a power saw.
Did we hear cicadas or katydids that night from the trees? According to evolutionary biologist Laurel Symes, cicadas ordinarily call during the day, while what we hear at night are crickets and katydids. The evidence points to katydids as our noise-making companions.
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