What kind of caterpillars are these?
Most likely it is Polymopheus moth caterpillar, known as Antheraea polyphemus  from the giant moth family.

yellow-green, and the setae become relatively less prominent with each molt. The translucent yellowish-green to green, full-grown (fifth instar) caterpillars are 60 to 75 mm in length. They have yellow mid-segmental lines that run from the sub-dorsal scoli (setae-bearing, wart-like bumps) touching the spiracles and to the lateral scoli on abdominal segments 2 to 7.

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The species is widespread in continental North America, with local populations found throughout subarctic Canada and the United States. The caterpillar can eat 86,000 times its weight at emergence in a little less than two months.

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The adult wingspan is 10 to 15 cm (approximately 4 to 6 inches). The upper surface of the wings is various shades of reddish brown, gray, light brown or yellow-brown with transparent eyespots.

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Adult male moth

Adult female moth