September evenings are alive with the sound of crickets, as males chirp rhythmically — and incessantly — to attract a mate.
In the East Bay, you're probably hearing Snowy Tree Crickets, also known as the "thermometer cricket," says Eddie Dunbar, president of the Oakland-based Insect Sciences Museum of California.
These are a group of small green crickets (Oecanthus sp., especially O. fultoni in the East Bay) that live in trees and shrubs. They produce a regular, rhythmic chirp that's surprising loud for an insect less than an inch long.
And yes, you can tell the temperature from the Snowy Tree Cricket's chirp, Dunbar says.
For the East Bay's Snowy Tree Crickets (and anywhere west of the Great Plains), use this formulafrom the University of Florida entomology department: "Count the chirps in 12.5 seconds and add 38 degrees." That will give you the temperature in Celsius. (You can convert Celsius to Fahrenheithere.) West Coast crickets chirp a bit faster than their eastern counterparts at any given temperature.
You'll hear the Snowy Tree Cricket mainly at night, but a relative — the house or field cricket (Gryllus sp.) — chirps during the day in the East Bay.
These large black crickets hide out in cracks and crevices under houses or may enter houses, Dunbar says. They have an intermittent chirp that is not steady or rhythmic.
Crickets don't chirp by rubbing their legs together, a common misconception. Instead, they rub the top of one wing along "teeth" at the bottom of the other wing, producing a sound called stridulation.
Both Snowy Tree Crickets and house crickets are active in the East Bay from spring through fall, Dunbar says.
Next month BugPeople will present "The Creeping Canvas" as part of the Friends of the Gardens at Lake Merritt annual fundraising gala at Lake Merritt on two consecutive evenings: Friday, Oct. 18 and Saturday, Oct. 19.