
These are sphinx moths in the genus Hemaris. The best that this botanist can tell, these are Snowberry Clearwing Moths (Hemaris diffinis). I took this photograph in Lake County, Indiana on August 7, 2010. Snowberry Clearwing Moths, which are found throughout almost all of North America, are said to mimic bumblebees, and it is pretty easy to see why someone unfamiliar with these lepidopterans might get confused.
In looking through my old photos, I found the two below of moths in the genus Hemaris.
I feel pretty good about calling the moth in the photograph above another Snowberry Clearwing Moth. This individual seems to fit the description well, with black legs and a very clean margin between the thicker black portion and the clear portion of the forewings. I took this photograph back in May of 2005 in St. Joseph County, Indana.
Here is another old photograph, taken in July of 2006 in St. Joseph County, Indiana. From the descriptions I have seen, I would call this a Hummingbird Clearwing Moth (Hemaris thysbe). This species has lighter-colored legs and a thicker, more ragged-edged reddish-brown forewing margin. As the name implies, Hummingbird Clearwing Moths are often mistaken for hummingbirds, as they hover over flowers while probing for nectar. They are found in North America but seem to be absent from the southwestern part of the continent.