Hemaris aethra

The H. aethra larva has multiple color forms, green being most common. It has bright red spiracles, a yellow prothoracic collar, and a caudal horn with a black apex fading to a pink-purple base; in contrast, diffinis larvae have black spiracles and the base of the caudal horn is bright yellow. Adults can be extremely difficult to tell apart from H. diffinis where they occur in sympatry, such as in eastern Ontario. Generally, aethra adults are slightly larger and more robust, and the dorsal thorax is a richer orange-brown color contrasting strongly with olive-brown dorsolateral stripes. The head is often greenish grey. The reddish-brown scaling on the apex of the forewings is generally larger and brighter red in aethra than diffinis, taking up 50% or more of the R4-R5 cell, and that on the hindwing anal margins is also more extensive.

Hemaris aethra ranges from Maine to northern Ontario, with occasional records as far west as Saskatchewan. Its geographic range is moderately broad (200,000-2,500,000 square km or 80,000-1,000,000 square miles) but is limited by that of Diervilla lonicera, its host plant. H. aethra is found in mesic, open deciduous forest, mostly in igneous bedrock plant communities, conditions that likely reflect the requirements of its host. In contrast, H. diffinis is found in more xeric, savannah-like habitats where its host Symphoricarpos is common. The separation distance for both unsuitable and suitable habitat is 1 kilometer. In addition to being sympatric with H. diffinis in eastern Ontario and possibly other areas, aethra's range overlaps with those of H. gracilis and H. thysbe.

Like other Hemaris species, Hemaris aethra is a dayflying moth. It hovers at flowers to feed on their nectar, pollinating them in the process. Adults have been recorded nectaring on Vaccinium, Chicory, and Lonicera tatarica. The only known host plant for H. aethra larvae is the northern bush honeysuckle (Diervilla lonicera). Native Lonicera species may also be larval hosts like they are for H. diffinis, but Lonicera are typically much less common than Diervilla where H. aethra occurs.

The specific name, aethra, comes from Ancient Greek Αἴθρα (romanized: Aíthra), meaning "bright sky". Several women in Greek myth bear this name; the exact namesake Strecker had in mind is not clear.