When Summer Comes Before Spring

Almost every year, LepLog readers have been fortunate to get a lesson in the complex Azure complex from one of the resident experts on azure classification, Harry Pavulaan. With his colleague David Wright, Harry helped re-jigger the entire spring lineup of these iconic lycaenid butterflies, and we have a new contribution to the many excellent pieces he’s written for LepLog. This one originated as a post on the Google Group MDLepsOdes.

Part of a mixed puddle party of azures and Silvery Blues in Green Ridge State Forest, March 2016

>> Harry writes:

The common name for Celastrina neglecta – “Summer Azure” – can rightfully be considered a misnomer.  But why was it called “Summer Azure” in the first place? 

Background:

Historically, it was believed that the Spring Azure (C. ladon) and Summer Azure (C. neglecta) were just different broods of the same species.  W.H. Edwards first described C. neglecta as a species, realizing it was different from C. ladon, which he re-described as Celastrina violacea.  [Thus, we now have the synonym C. ladon (=violacea)]  Edwards conducted several years of rearing trials and later changing his mind and believed his “C. violacea” and neglecta were just spring and summer broods of the same insect.  His rearing experiments had one major flaw, which David Wright and I learned the hard way back in the 1980’s: ANY univoltine Azure raised indoors from egg or first instar caterpillar, through to the chrysalis will produce a FALSE second generation later that same season.  So, Edwards was confused by his own rearing.  His false second-generation Spring Azures produced adults that looked superficially like the Summer Azure.  [He also considered the Appalachian Azure (now known as C. neglectamajor) part of a multi-brooded Azure.  Wrong again.]  Many have continued to follow Edwards to this day. 

So here is why “Summer Azure” is a misnomer.  Back as recently as the 1980’s, Dave Wright and I, through many rearing trials, learned that the Spring Azure (C. ladon) does NOT produce the Summer Azure.  The main difference is that Spring Azure males have a wing scale structure that is unique among all Azures (except the Sooty Azure, C. nigra).  This wing scale structure breeds through 100% of the time to the next generation, and so on.  However, up until the early 80’s, the Spring Azure was very common in the eastern U.S., using Flowering Dogwood as its primary host.  I remember finding Spring Azures in huge puddle parties at places along the Potomac River and at McKee-Beshers WMA.  The Summer Azure was primarily a multi-brooded Summer insect that first emerged in May and did not produce an earlier full spring brood except for occasional individuals emerging in winter or in March.  In New England, there was no spring brood of the Summer Azure at all and early July was the first time one would see Summer Azures annually.  Nobody ever before seemed to notice that winter individuals in the Washington D.C. region had a different wing scale structure from the Spring Azure.  We all thought that they were all C. ladon!  Once David Wright did some microscopic analysis of the wings in the 1980’s, we suddenly realized that there were TWO Spring Azures in our region: univoltine ladon with the unique wing scale structure and multivoltine neglecta with “normal” Celastrina wing scales.

The Spring Azure went into rapid decline with the demise of Flowering Dogwood starting about 1990.  It appears that, being highly adaptable, the Summer Azure moved in to replace the Spring Azure in its springtime niche.  Since that time, the Summer Azure has produced a full spring brood in this region and is now our common “spring” Azure.  The original Spring Azure (C. ladon) is now quite rare in the Piedmont region.  Spring Azures are still fairly numerous in places like Green Ridge where the caterpillars feed on Black Cherry flower buds, flowers and fruits, rather than Flowering Dogwood.  Similarly, Spring Azures have adapted to using American Holly on the western shore side of the Chesapeake Bay.  But in both places, it flies with the Summer Azure’s spring brood.

Uppersides (males only) of six mid-Atlantic spring-occurring azure species [Courtesy Harry Pavulaan, 2016]

Key:

Top Row: (left) C. ladon, Spring Azure; (right) C. lucia, Northern Azure

Middle Row: (left) spring form C. neglecta; (right) C. serotina, Cherry Gall Azure

Bottom Row (left) C.  idella, Holly Azure; (right) C. neglectamajor, Appalachian Azure


So, the confusion over which species flies earlier, Spring or Summer Azure, is easily explained by referencing historical treatment of Azures in most all of our field guides until a few years ago.  Some of the more recent state guides have an accurate description of Azure relationships: Pennsylvania, Indiana, North Carolina (online).  Older guides will tell you that Spring Azure flies first, then later comes the Summer Azure (and, erroneously, they’re both broods of “C. ladon”).  This is now an outdated view based on flawed information dating back to Mr. Edwards.  Now we know that the Summer Azure produces a full earlier flight than the Spring Azure.  The Summer Azure is actually a year-long Azure.  I have documented them from February to November but there have been reports in Dec. and Jan. by others.  Most years, they peak in late March, but a few years ago, they flew in large numbers here in Leesburg, VA. throughout the month of March, then finished their flight around April 1, only to reappear during the second annual brood in May.  One single Spring Azure was documented in early April that year.

I hope this clears up why people are confused over why Spring Azure is not the first Azure on the wing.  Rick is correct that many naturalist sites have not caught up with science, and the Azure complex is outdated in many past guides, and some groups (in particular NABA) use their own approach which, frankly, puzzles me. 

Harry Pavulaan

P.S. – I will write up a short paper on the above topic with detailed images sometime this year.  Hopefully I can get it published by Banisteria by next winter.  Banisteria is now free, open-access, online, and better since you don’t have to be a subscriber to read issues.


This entry was posted in general butterfly news, Identification tips, taxonomy. Bookmark the permalink.

2 Responses to When Summer Comes Before Spring

  1. John Turner says:

    A very interesting article that helped to clarify these two species. To be clear, are the first azure butterflies I’m seeing on Long Island, NY Summer azures and not Spring?

    • Rick says:

      I’m not sure, John. A question better put to Harry, who is working through all the permutations of various populations on the East Coast. This piece accounts for the situation here in the mid-Atlantic but the timing may not be accurate for other areas.

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