Gypsy Moth caterpillar

Lymantria dispar dispar, commonly known as the gypsy moth, European gypsy moth, or North American gypsy moth, is a moth in the family Erebidae that is of Eurasian origin.
Larvae (caterpillars) emerge from egg masses in the spring. Most larvae hatch within a week, but can take as long as a month. The new larvae remain on or near the egg cluster if they hatch in rainy weather or if the temperature is below 7 °C. The larva will disperse even if there is enough foliage for growth, hanging from silk threads and waiting for the wind to send them aloft. The larva are about 3 mm long when they first hatch and will grow to 50 or 90 mm.