North American Field Crickets
Summer nights are filled with the sound of field crickets (family Gryllidae).
Many species are so visually similar they are best identified by their chirps. The sound is produced by rubbing the sharp edge of one forewing (usually the right one) against rough teeth spaced along a vein on the other; only males have these structures.
Females have special “eardrums” on their forelegs called tympanum, with which they detect the calls of males. Female crickets can be distinguished from males by the presence of an ovipositor that they lay eggs under the soil with - males have only two appendages on the abdomen, while females have three (the long central one is the ovipositor; this is a female).
Field crickets are omnivorous, feeding on seeds, fruit, and small insects, including the eggs of other invertebrates.
photo by Mr.TinDC on Flickr
(via: Peterson Field Guides)