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MARY LOZIER: This time of year, the songs of thousands and thousands of insects are a persistent undertone to all the noise of the city. Most people know what crickets sound like, but listen closely to a late summer night and there are other sounds as well. Many people know how to identify birds by their songs. And for those who don't, there are audiotapes of bird songs and even frog calls.

But insect calls are a different story. Most people aren't all that fond of bugs, and there aren't any readily available tapes to identify insect sounds. Still, with a little basic knowledge, you can begin to them out. The chirping you hear in your basement is probably the common house cricket, a European import. If a similar chirping sound is outside in the daytime, it's likely to be a field cricket.

[CRICKET CHIRPING]

Field crickets are those black ones you find under the trash can or hiding beneath rocks or sitting in tall grass. They sing during the day and on into the night from near the ground like this.

[CRICKET CHIRPING]

At night, the tree crickets begin to sing. Although individually, they make the same chirping sound that field crickets do, the chirps often blend into one long trill like this.

[CRICKET CHIRPING]

You may have heard you can tell the temperature by how fast crickets sing. That's true for one particular species, the snowy tree cricket, which is common in the Twin Cities. It's pale green with transparent wings, usually found singing in smaller trees and bushes. If you count the number of chirps it makes in 15 seconds and add 40, you get the temperature in degrees Fahrenheit.

[CRICKET CHIRPING]

Grasshoppers also sing in the fall, but their sound is more raspy and less musical than the crickets call. Crickets make their songs by rubbing two sets of wings together. Grasshoppers by rubbing their legs against their wings.

[GRASSHOPPER BUZZING]

Along with the calls of crickets and grasshoppers, there's another inescapable late summer insect, call that buzzing high wire sound that is everywhere in the city, a background to all the neighborhood noises.

ROBERT DANA: Well, I don't think that you can mistake a cicada for anything else.

MARY LOZIER: Robert Dana is an ecologist at the State Department of natural resources with an interest in insect calls.

ROBERT DANA: It's loud. It builds up in a kind of billowy crescendo to my ear. It's a very distinctive and I think the most characteristic sound of summer that I know of.

MARY LOZIER: Cicadas are fat, black, and green, vaguely grasshopper looking insects about 2 inches long. The adults live in trees and feed on tree sap, which they pump from the twigs with their big soda straw like mouth parts. They call by vibrating drum like membranes on the sides of their abdomens. If you've sorted out all those sounds, crickets, grasshoppers and cicadas, there's still one more.

[KATYDID CHIRPING]

When you get a katydid in your neighborhood, you'll know it. They begin to sing at dusk and continue all night. They make their sound by rubbing the overlapping bases of their two front wings. They amplify the sound with a tiny speaker, a tightly stretched area on the upper wing that acts as a resonator. The result, says Shoreview Homeowner Karen Iverson, is very annoying.

KAREN IVERSON: It starts right when it gets dark between 8:30 and 9 o'clock at night. Religiously, it starts, and well, last night, it went till 2:00 the morning. I don't know if I fell asleep or if it stopped, but I closed my bedroom window, which is right next to the tree. I turned the fan on and had a pillow over my head, and I still heard it. So constant, never stops.

MARY LOZIER: It's hard to see a katydid up in the trees because they're grass green in color and their wings look like leaves. Karen Iverson hasn't had any luck either finding or dislodging her katydid.

KAREN IVERSON: I don't know if I should tell you this, we used everything. I shot the hose up there to try and knock it down. I didn't know if it was a flying thing or a ground thing. Shot the hose up there, that didn't take care of it. The neighbor boy climbed the tree and shook it, still kept squawking. And what else do we do? Oh, we shined a flashlight up there. We threw rocks up there. We threw apples, and we tried a bottle rockets and nothing. It just kept going.

MARY LOZIER: Iverson says she's going to keep trying to catch the katydid. In any case, it will be silent soon when the frost comes. For now, it and all the other singing insects fill the warm summer nights calling for a mate in the short time they and the summer have left. For the FM news station, I'm Mary lozier.