Hemaris thysbe is the largest of the three "clearwing" sphinx encountered in Massachusetts.
Hemaris thysbe does not have the much more contrasting yellow abdominal segments suggesting a bumblebee as in the much smaller Hemaris diffinis. The outer dark wing margins are also much narrower in H. diffinis, and there are black lines on the ventral surface of thorax of H. diffinis.
The side shot of Hemaris thysbe shows off-white dorsal leg colouration and an absence of the dark red bands on the underside of the thorax, present in Hemaris gracilis.
Hemaris diffinis, Tom Gagnon's verbena plantation, Northampton, courtesy of Barbara Spencer.
In the above image of H. diffinis the very narrow dark margins of the hindwings are especially visible.
In the ventral shot to the right, the black lines on the thorax are well ilustrated.
The dorsal surfaces of the legs are also black.
Hemaris diffinis, courtesy of Barbara Spencer.
Those Sphingidae west of the continental divide (western Montana, Idaho, Washington, Oregon, Nevada, Utah, California, Arizona, western Wyoming, western Colorado, western New Mexico), previously thought to be H. diffinis are now determined to be the recently elevated species, Hemaris thetis. It is my understanding that the moths described as H. senta also belong to H. thetis as thetis was described (Boisduval, 1855) before senta was described [Strecker, 1878].
Subsequently thetis was synonymized with diffinis, but, based on paper by Christian Schmidt Journal of the Lepidopterists' Society 63(2), 2009, 100-109. Hemaris thetis (Boisduval, 1855) (Sphingidae), H. thetis in now recognized as a distinct species, based on DNA and genitalia analysis.
In some places just East of the Divide (Colorado, Alberta) overlap of ranges of H. thetis and H. diffinis is known and precise determinations, by photographs only, will be next to impossible.
Thanks to Edna Bottorff and Ryan St. Laurent for alerting me of this change. It will be a little while before I get the changes made on the Sphingidae of the Americas website.
Hemaris gracilis, Cummington, Massachusetts, June 9, 2004, courtesy of Barbara Spencer.
Hemaris gracilis is intermediate in size between the larger thysbe and the smaller diffinis.
Note the dorsal red colouration of the legs and the red areas on the ventral surface of the thorax.
Dorsally the abdomen is red.
The dark outer wing margins are wide as in H. thysbe, and, abutting the hyaline (clear) area, the margins are smooth as opposed to irregular in H. thysbe.
Another note regarding the distinction between thysbe and gracilis: In H. thysbe, the greenish "fur" of the thorax continues to the sides and meets the thin black line that runs through the eye. In H. gracilis, the greenish "fur" does not extend below the wing juncture with the body. Instead there is a whitish band followed by the characteristic red band along the side of the abdomen.
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