I’ve been observing duskywings here in New Hampshire for a while. Five species are known to fly in the state: Juvenal’s, Dreamy, Sleepy, Wild Indigo, and Horace’s Duskywings.
To my eye, nothing in their flight behavior has clearly stood out as a reliable way to distinguish them in the field. I’m wondering—has anyone noticed consistent differences in the way these species fly that could help with identification?
Any insights or field-based impressions would be much appreciated!
Hmm, that’s a good question. I’ve been studying butterflies for about 50 years, and have seen my share of duskywings in flight. Not just in the Northeast, but all across North America. After considering this, I honestly can’t think of one species that can be consistently distinguished by flight behavior alone. The only thing that comes to mind is the perception of relative size in flight, such as very small lucilius vs. large juvenalis. As for differences in the flight, I’ve not noticed anything that stands out. In fact, I sometimes find it difficult to even distinguish cloudywings from duskywings when there are several of each occurring together (such as in Florida).
That being said, duskywing males patrol for females, but some more vigorously than others. For example, juvenalis males fly rapidly and wildly about, while baptisiae males seem to search more deliberately, bobbing and weaving through the vegetation with more “purpose.” However, I’m not sure I would hang my hat on this behavior to discern species, since this behavior is likely influenced by size, gender, habitat, and number of individuals present. When many adults of the same species are present, they seem to be less wary and often fly less rapidly (“safety in numbers”). Also, females fly differently than males, with the former tending to be more retiring, particularly when searching or oviposition sites. Males also puddle, while females do not.
In summary, it’s not been my experience that one can consistently distinguish duskywing species based on flight behavior.