Weather has been very cool and wet. Smerinthus jamaicensis closely resembles Smerinthus cerisyi, but jamaicensis is much smaller with larger blue patches on more vibrant and deeper purple in lower wings. The Twin-spotted sphinx is single brooded in the northern portions of its range with moths on the wing from early June to early August. In the southern portions of its range there are two broods with jamaicensis moths on the wing from late May through November.
Moths eclose at night from subterranean pupae which have wiggled to the surface.
The females call the same night and pairing can last for up to twenty hours. Pale green ova are deposited singly or in pairs on host plant foliage. Larvae feed upon many forest trees including birches and cherries, but are expecially fond of poplars and willows.