Dr David Wright, who along with Harry Pavulaan is the authority on eastern species of Azures, kindly commented on this genus for BugGuide. The North American members of this genus are now divided into 8 species. In the east, every state has sympatric species (i.e., occurring together) varying from 2-5 species per state. For a postive identification it is important to know which species fly in the locality, their flight dates, and whether or not for the Spring-flying species it is an "early", "normal", or "late" Spring. Habitat is also of importance, and a dorsal view (often impossible to get a photo of) is very useful for ID. Many of the species have individuals of several forms, i.e., they are polymorphic, on the underside that have been named "lucia", "marginata", and "violacea". Thus these forms, per se, are of little/no use for identification purposes.
The commonly-used species epithet, ladon, for most of these species in texts is unfortunate and incorrect. Celastrina ladon is a species restricted to the Appalachian and Ozark ranges. It has a unique scale arrangement on the fore wings - long overlapping scales - clearly shown in Fig. 21 of Wright & Pavulaan (1999).
See updates by Schmidt & Layberry 2016 (1)
and Pavulaan 2014 (2)
The following quote by Harry Pavulaan was originally posted here
in "Forums: Taxonomy Proposals" by Tom Murray, 14 January 2006.
"Several people have inquired with me offline regarding the status of the Cherry Gall Azure paper. First, here is the reference:
Pavulaan, H. and D. M. Wright. 2005. Celastrina serotina (Lycaenidae: Polyommatinae): A new butterfly species from the northeastern United States and eastern Canada. The Taxonomic Report Vol. 6(6):1-18. The paper fully describes and officially names the Cherry Gall Azure.
Copies can be ordered for $10 each from me (via email) but you will have to wait for about 2-3 weeks so I can have a run of copies printed and mailed from Virginia. PDF copies are available more rapidly at $5 per upload (this helps support our continued research).
The Cherry Gall Azure has become accepted as a species in many publications since we first recognized the distinctness of this butterfly in 1983. I first noted this butterfly in my field studies when I lived in Rhode Island in 1983 and 1984, and have studied it ever since. Many authors did not wait for us to officially describe and name the butterfly, thus it is variously treated as "Cherry Gall Azure (Celastrina sp.)" in books such as Butterflies of Canada, Butterflies of Quebec. The name "C. serotina" is now available as the latin name. The species "type locality" is Great Swamp WMA in West Kingston, R.I. where it can be seen in profusion along trails in mid-May.
There are three full species of Azure in Massachusetts, possibly four. None of these are "subspecies" of each other since each one is essentially univoltine and does NOT produce any of the other seasonal flights. By month:
The April emergence in most of Massachusetts is C. ladon (Spring Azure). This is the array of dark forms ranging from dark patches, margins and large spots. In the high elevations of Berkshire County, C. lucia (Northern Azure) can be found. In the northeast, the undersides of C. ladon and C. lucia are identical in their range of variation. In other words, they cannot be distinguished by their undersides. However, the uppersides of C. ladon and C. lucia males are dramatically different in the structure of their wing scales, easily discernable to the trained eye.
The May flight is C. serotina (Cherry Gall Azure). These are the butterflies that are very white beneath, with very crisp and distinct black spots. The upperside is similarly distinct from C. ladon and C. lucia.
The July flight is C. neglecta (Summer Azure). This familiar butterfly has no biological connection to any of the earlier flights. All Azures seen from July 1 onward are C. neglecta. There is a partial second brood in early September some years, but only a small number of adults are reported.
The Appalachian Azure (C. neglectamajor) likely exists in extreme southwestern Massachusetts, in association with stands of the hostplant Cimicifuga racemosa. However, nobody yet has investigated this as a possible new addition to the Massachusetts fauna!
NABA treats several species of Azure (C. idella, C. humulus, C. neglecta) as "subspecies" of the Spring Azure, but this is flat out wrong, as subspecies are GEOGRAPHICAL races, not seasonal flights. Virtually all biologists recognize the fact that subspecies cannot be found in the same places but at different times of year. I suspect, that by previous example, NABA will similarly refuse to recognize this unique butterfly as a species."
- Harry Pavulaan
Wright, D.M & H. Pavulaan. 1999. Celastrina idella (Lycaenidae: Polyommatinae): a new butterfly species from the Atlantic Coastal Plain. The Taxonomic Report 1(9): 1-11