For a long time, we have observed our favorite (California gray) squirrel scratching herself but never saw evidence of any parasites on her, until recently, when small insects started crawling off her, one or two during each visit.
The insect does not appear to be any kind of flea or tick, based on the images of fleas and ticks that we can find online. The insect is a kind of golden-reddish brown in color. It crawls slowly. It does not jump. It is much longer than it is narrow, a little longer than an eighth of an inch, I would say. It seems to be covered with a piece of shell-like material, bent along the center, like a middle piece of arched roof. It is extremely durable and resistant to being crushed.
Does anyone have any idea as to whether a drop of advantage II for small cats at the base of the neck might be helpful? I've heard that only "revolution" is intended to cover a wide range of parasites, while advantage is only intended for treating fleas, but this is apparently only available through a veterinarian's prescription, which we would probably have difficulty obtaining (for reasons I can explain if that would be helpful).