I see these guys a lot in the spring, on the back deck.

They change from very dark brown (almost black) to a light brown,
then change to a lime green. They seem to communicate by
twitching their heads up and down. There's a pink and white disk
that forms underneath the neck of the one sex. I'm guessing this
is a male, and about 3" long (not including tail).

The females (?) are much smaller (2" body), and don't seem to
change color, nor do they have the disk that I've noticed.

Anybody? They must be pretty common around here. I see 'em every
year.

-sw