Azure Butterflies

There are lots of butterflies in NJ that look similar [1] though most of the time there are subtle differences that allow them to be identified (even if it requires getting a better look than the butterfly provides to you). But I'm not confident this can be done with the Spring Azure, Summer Azure, Lucia Azure, and Appalachian Azure. They (and other) species are small butterflies with light, speckled underwings with (at least for males) bluish-purple upperwings, and without the "tails" and orange spots associated with Eastern Tailed-blues. 

Although today these butterflies seem to be recognized as separate species in a Spring Azure Complex (where a complex is a set of related species that are difficult to differentiate) there have been times in the past when they were all considered one species with different broods and with regional variations. 

Having said that, some lepidopterists appear to have detected subtle physical differences between Spring and Summer Azures, and believe most of the "Spring Azures" we see today are actually Summer Azures that are emerging early in the season ever since Spring Azure populations declined. (It's unlikely the wing scale structure differences can be detected in the field, but if you've got a microscope and a surprisingly cooperative butterfly with you, this works great.)

This article suggests 5 different ways to differentiate these butterflies; I mostly do the 2nd easiest one: Call them Spring Azures from March-May and Summer Azures from June-September. This has the downside that if I photograph the exact same butterfly on May 31 and June 1, I'd classify it differently on these dates. (The article does suggest that if you see a faded/tattered winged azure in early June, or an obviously fresh-looking azure very late in May, you could reverse the identifications. A lot of times though I have enough trouble figuring out that it's not an Eastern Tailed-blue, let alone evaluating age.)

TL;DR: Nature doesn't always make things easy for us.


Spring Azure
May 5, 2022 at the Plainsboro Preserve
Photo 18260140, (c) jpviolette, some rights reserved (CC BY-NC)


Summer Azure
August 3, 2022 at Lord Stirling Park
Photo 222581816, (c) jpviolette, some rights reserved (CC BY-NC)


[1] Think about (Eastern Comma, Question Mark), (Orange Sulphur, Clouded Sulphur), (Painted Lady, American Lady), and (Monarch, Viceroy) pairs.

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