Need help ID'ing a caterpillar

[The Fleck Family]

I live in southeast Michigan and today my son found a large (9-10 cm)
green caterpillar.  I'll try to describe it more accurately:

Length: 10 cm
Diameter: 1.5 cm
Markings: overall bright green.  The first 3 segments have 2 symmetrical
dorsal protrusions colored orange with black specks.  The next 7
segments have 2 symmetrical yellow spikes.  The final segment has blue
spikes.  Each of the segments has smaller blue spikes protruding from
the sides.

Any ideas?  Thanks...

Chris