It's possible these individuals from Lyons, Colorado, are darker due to dark pines in the area (i.e. Ponderosa Pines).

I studied characters of O. pini from Wisconsin, and was very surprised to find yellow on the face, whitish patches behind the 'knees' and whitish fields on which the black antennal markings sit -- the three characters that seemed to be unusual on the Lyons tree crickets!

I suspect they are darker due to the dark bark of Ponderosa Pines in the area. Even though none of the 5 individuals in the photos were found on pines, I did hear slow trilling up in conifers in the Lyons area, and I do often find O. pini on other vegetation here in SE Wisconsin (Milkweed, Aster, Goldenrod).

Even though this is very likely not a new species, it is still quite interesting.

Moved from Undetermined species - special interest.

I visited the Lyons area early this week and managed to find one male and one female which match the general color in your photo. The male I found is not as dark, but has the same colors on the head. They have many unique features, I'll post photos soon. I'll be investigating these two newly found tree crickets thoroughly and analyzing the male's song.

Pretty confident this is a new species. Thank you for posting this photo - one of several photos on BugGuide which sparked my interest and led to determination of a new species! I'll keep you posted - the description paper not likely to be completed until 2017.

I was able to visit Lyons, and found 1 male and 1 female with these exact characteristics (that also match those of two other photos from Lyons). I'll be analyzing recordings and will post here the results.

One was found on a shrub and the other on a sunflower of some type.

Moved from Pine Tree Cricket.

I'm not commenting specifically to anyone, but hopefully this will be useful.

Traditionally O. pini is an eastern species. The name used for Colorado has been O. nigricornis. I don't know what is correct, but the name "pini" in colorado does raise the eyebrows a bit. In Colorado, I've only seen these dark ones in weedy growth and sometimes shrubbery. Lyons is at the edge of the Plains, where a two canyons join and cut through the first rank of "hogbacks". Depending on where you are there are no trees, some trees, or there is forest (mostly the trees listed above, or Cottonwoods, Willows, Russian Olives, or street and yard plantings). Up in the mountains there is a lot more variety in woody plants and some of these Tree Crickets stick pretty much to the hills, not reaching out into the Plains much (or at least not past the Front Range towns full of exotic plants). I assume "northwest of Lyons" is in the mountains along the North St. Vrain (???). When I was a kid, I thought these dark ones were just the same as all the other ones in the "weeds" (the first two mentioned below), and just sometimes darker (mostly in the mountains). The two are supposed to have different songs, but I'm not confident that I could tell which was which without conscious effort, they sound very similar, differing mainly in pitch (plus the pitch, volume and speed of the song vary with the temperature). Most of the Tree Crickets sound pretty similar unless you are listening for the differences.

Other species in the area (but they all look different from the dark ones) include the very closely related O. argentinus & quadripunctatus (which I've never been able to draw a line between, not even with my ears - they are very common all over the place there, but usually not up in the trees); O. fultoni (which lives in the trees along watercourses and in towns - the ones with pulsed songs that you supposedly can tell the temperature by); and O. califoricus (perhaps it is limited to Junipers in that area - I saw very little of it when I was growing up, but it was usually in the same area in the foothills where there are Junipers, and further south Pinyons; t sounds a lot like most of the others.

Moved from Common Tree Crickets. Definitely in the nigricornis species group. I'm putting it in the O. pini section for now - based on the brownish tint to limbs and head, and I believe a pink-tinged eye.

Pine tree crickets in Wisconsin tend to have more of a rusty color than brown. What type of conifers are in your area? Do they have deep brown or black bark?

Moved from Tree Crickets.

Moved from ID Request.