I looked at the guide's images but could not find an exact duplicate.
I'll try some more tomorrow
Thank you for your help.
Michel

How about considering the packard grasshopper or Melanoplus packardii? I think the extreme western boundary of its range actually cuts through the valley you're living in; they have well-developed wings, large eyes, and many are coloured just like your specimen; and they're big, classed right up there with the two-striped and differential. Unfortunately, I can't quite make out what's going on with your fellow's male parts, especially since he seems to be flexing things a bit, but the overall look back there seems about right. Following are a couple of links to good photos of this species (their colouring does vary regionally so you'll have to look past it a little)...see what you think. Be advised, however, that if you've got packard grasshoppers, then you should also have the closely related striped sand grasshopper or Melanoplus foedus...there's considerable size and appearance overlap with the males of this species and you apparently have to closely examine a male's genitalia in hand to say for sure which is which. Your specimen's being a real big, dark one and living in a (presumably) well-vegetated area does argue towards this being a packard, though...

Packard grasshoppers:
http://www.sidney.ars.usda.gov/grasshopper/ID_Tools/F_Sheets/packard.htm
http://www.opsu.edu/UnivSchools/ScienceMathNurs/PlantsGrassh/grasshoppers/files/m_packardii.html

Striped sand grasshoppers (first site shows how to differentiate males from packards...NOTE that adult male/female images are mistakenly reversed):
http://www.sidney.ars.usda.gov/grasshopper/ID_Tools/F_Sheets/strpsand.htm
http://www.opsu.edu/UnivSchools/ScienceMathNurs/PlantsGrassh/grasshoppers/files/m_foedus.html

thank you for your help. I looked at the photos in the websites above. The individual on my image looks greener wether that means anything or not. Our backyard is well-vegetated so I guess Packard's would fit.
I took a photo of another one a at Ankeny NWR in a sandy area. The subject sit vertically on a stem but, unfortunately only the image i does not reveal anything that could help. I'll look for them again when I visit next. Again, thank you
Michel Kleinbaum

Next time you see a similar male grasshopper (or maybe even this same one), do try catching him and having a real close look at his external genitalia before you do anything else. It should help narrow down your species ID a lot, even if it's just to rule out a possibility or two. It'd be funny if he turned out to be your basic two-striped after all this--there's just something still niggling about the look of his hopper butt. On the other hand, with one exception (a very black melanistic specimen), I've yet to see a two-striped grasshopper that didn't have at least a faint trace of its usual definitive striping, from behind its eyes all the way back onto its wing covers. This one's striping seems to definitely stop partway across his thorax, at least on my monitor's screen.

I'll try catching but I'm afraid that, at 80, I am not as nimble as I once was. Getting on my knees to photo isn't too bad, getting up is another story. Thanks again
Michel Kleinbaum