White-marked Tussock Moth Caterpillar

Caterpillars are recognized by the bright red head and broad black stripe along the back flanked by a yellow stripe each side. Two red glands on sixth and seventh abdominal segments, and four tufts of hairs (which may be white, gray or yellowish) on the first four abdominal segments are common to several members of the genus.
CAUTION: Contact with hairs may cause an allergic reaction; Bugguide.net