Black-horned Tree Crickets are named for their black or blackish antennae. Some individuals have striking black heads, pronotum and limbs as in this photo.
Some, however, have only a bit of black on their limbs, a streak of black on their head and pale black antennae.
O. nigricornis is ID'd by the markings on the first two segments of their antennae.
The scape (1st segment) has a long vertical black mark medially and a shorter horizontal mark at the top. The pedicel (2d segment) has two vertical black marks which are either adjacent or taper at the bottom to form a V.
Note: O. nigricornis and O. forbesi are virtually impossible to separate in the field. The best indicator is counting the pulses of the song of the male at a known temperature. The rate of O. forbesi will be faster than O. nigricornis at the same temperature.
Although any color patterns are possible in both species, individuals with deep black limbs tend to be placed in O. nigricornis here at BugGuide:
Northeast U.S., from Minnesota, Iowa, Missouri to Maine, including southern Ontario and Quebec. A branch follows the Appalachian Mountains down to North Carolina and Tennessee. (1)
Singing Insects website extends this range west to Montana.
As of 1/2009 the range map on SINA shows occurrence in the area from Montana south to Colorado then east to North Carolina then north to Maine and back west to Montana. The map also includes the extreme southern portions of Alberta, Saskatchewan, Manitoba, Ontario and Quebec.
Tree crickets do not dwell on the ground. Despite their name, this species of tree cricket does not dwell in trees. Black-horned Tree Crickets are found in vegetation -- sometimes close to the ground, but usually 1-4 feet above the ground. They are commonly found on Goldenrod, thistle and tall grasses, but also on a variety of plants, weeds and shrubs.
Tend to hatch in June and mate from August to October.
Undergo a paurometabolous development (Gradual Metamorphosis). Nymphs resemble small adults and gradually develop external wing buds. They live in the same habitat as adults, typically taking the same food.
A great source for 'everything you ever wanted to know about tree crickets' is an article written in May 1915 by Bentley B. Fulton in a Technical Bulletin for the New York Agricultural Experiment Station. The Tree Crickets of New York: Life History and Bionomics
Forbes Tree Cricket; Prairie Tree Cricket.
Capinera, p. 205 (antennal markings illustration), pp. 208-209 (brief description and range map) (1)
Tree Crickets - information and photos