Northern Prairie Wildlife Research Center
Stocky, bright green with 3 narrow yellow dorsal saddles on first, fifth, and eighth abdominal segmentsthese sometimes edged anteriorly with red and black spots. Dorsum of second thoracic segment with closely set red tubercles. Handsomely dappled with yellow spots; red spotting may surround spiracles. Abrupt brother (R. abrupta), co-occurs with R. frater but tends to be far less common. Food: especially poplars but also alders, birches, and willows. Caterpillar: June to September; apparently 1 generation.