Length 13–15 mm (Bay Area, California, 10–14 mm). Outside marks on first and second antennal segments usually less heavily pigmented than inside marks; outside mark on first segment often round; tibiae and apex of hind femur usually without conspicuous dark markings; more than 47 teeth in stridulatory file.
Fast-calling tree cricket—Outside marks on first and second antennal segments as heavily pigmented as inside ones; outside mark on first segment never round; tibiae and apex of hind femur with conspicuous dark markings; width of inside dark mark on first antennal segment less than distance between inside and outside marks; fewer than 50 teeth in stridulatory file. Prairie tree cricket—black marks on second antennal segment confluent, contiguous, or separated by no more than one-third the width of the inside mark.
Open areas, including roadsides, old fields, and crops. Mostly on herbaceous plants but males sometimes call from the lower limbs of trees or shrubs.
One generation annually in the north with adults occurring from late July or August until frost. Two or more generations annually in the south with first generation adults appearing in May near Gainesville, Florida, and in June near Raleigh, North Carolina. In Gainesville, adults occur through December. Farther south in Florida, adults occur year round.
The five herb-inhabiting species of the Oecanthus nigricornis species group—the four-spotted, prairie, black-horned, Forbes's, and fast-calling—are the most commonly encountered and the most difficult to identify tree crickets.