Identification
This species usually has a yellowish head. The antennal markings are very similar to Black-horned Tree Cricket. A vertical black strip on the medial portion of the scape (1st segment) and a shorter horizontal teardrop shape on the upper portion of the segment. Two horizontal marks are separated by a space on the pedicel (2d segment). Forbes' and Black-horned are very difficult to ID -- only the pulses per second (p/sec) of their song can distinguish one from the other. Forbes' pulses per second raises on hot days and lowers on cooler days; while the Black-horned TC's song remains fairly constant. On an 80+ degrees day Forbes' pulses per second will be approximately 80 p/sec and on a 60 degree day their call will be approximately 60 p/sec.
The female has a green body.
The male usually has a darkened strip in the center of the pronotum.
Range
As a general rule, Forbes' is found west of Ohio; Black-horned is found east of Ohio. They are best ID'd by the rate of the male's song.
Habitat
Similar habitat to Black-horned Tree Cricket -- low to the ground on various plants. May be found in low to the ground branches of small trees.
Season
Tend to hatch in June and mate August to October.
Life Cycle
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.
Click on an image below to view the Life Cycle:
Female
Male 
Remarks
This is a sonogram of a male Forbes' tree cricket singing:
See Also
Black-horned Tree Cricket; Prairie Tree Cricket; Four-spotted Tree Cricket
Internet References
http://oecanthinae Tree Crickets - information and photos
http://buzz.ifas.ufl.edu/594a.htm Singing Insects of North America