A Tale of Two (or More) Crescents

2018 May 25 northern crescent 1 in situ_MD-Indian Springs WMA-Indian Springs Pond copy

Field or photo ID for the non-tharos crescents is only accurate for the males as the females of all our species in MD are indistinguishable in the field except by association with known-species males. [this one photographed 2018 May 25, Indian Springs WMA, so likely one of the bivoltine cocyta-group crescents if it sports an antennal club that is fully orange underneath — this one did, see below]

Oh for the simple days when in the mid-Atlantic region if you saw a crescent you could safely assume it was the common, indeed almost ubiquitous, Pearl Crescent (Phyciodes tharos).  The only doubt to contend with would be if you saw windows in the black spots on the trailing edge of the hindwing to make it a Silvery Checkerspot.

But no, we had to go poking around looking at flight behavior, timing of broods, and minute differences in color of the antennal clubs and go confusing ourselves with multiple crescent possibilities.

So what are the crescents we can expect in the area?

Of course Pearl Crescent is still the go-to orange-and-black small butterfly of choice for most of Maryland most of the time.  Like many crescents, the wing pattern is highly variable, as is the amount of orange on the antenna.  Many older accounts say there is one continuous, rolling flight of Pearl Crescent from early spring until frost, and in fact you can find crescents in the field almost anytime during the summer season. Many good authorities still think all our crescents are Pearls, Phyciodes tharos.

Harry Pavulaan begs to differ.

I asked him recently to give us the lay of the land, crescent-wise, for the MD-VA-WV region and help us figure out what to look for in the field in 2023.  He and colleagues have been working on the complicated relationships of the, um, complex (in every sense of the word). Here’s his capsule summary of what we know — and don’t know — about our crescents.

Harry writes…

Our present understanding, via published literature, is that there are two active species of Phyciodes present in this region:  P. tharos and P. cocyta (often known by other names).  P. batesii is certainly not present.  To the best of our knowledge, P. cocyta consists of two species in our region: a univoltine taxon (P. cocyta) that flies in the higher mountains in late June to early July; and a bivoltine species that flies in the mountain region as far east as the Frederick Municipal Watershed, in May and again in August.  This has not been published, but is the subject of considerable field observation, collection and rearing, and is now being analyzed by Nick Grishin’s genome research team at Univ. of Texas, Southwestern Medical Center. 

Distinguishing these three species is a considerable challenge.  The females are indistinguishable because females of all three species are identical in morphology and their antenna clubs all vary from black to orange.  In specimen series, tharos females are smallest, the bivoltine cocyta females are slightly larger, and univoltine cocyta females are the largest.  Photos won’t do any good and are only identifiable to genus (Phyciodes), though one can get them in the ballpark by flight date.  Females are best identified by association with males within population concentrations.

The males, on the other hand, can be distinguished only by a single character: the lower (ventral) side of the antenna club.  P. tharos males have black antenna clubs with some gray on the lower side.  Some P. tharos males have a slight orange tip on the upperside of the club, but the underside of the club is not orange.  P. tharos often lives in concentrations around aster hostplants and fly in April, July and September, though their flights can vary somewhat from year to year.

The males of the two P. cocyta species (univoltine and bivoltine) are indistinguishable except by size and flight date.  The male antenna clubs of both are orange beneath.  The orange may also appear on the upperside of the clubs, but extends across the entire lower side.

Several field guides suggest that P. tharos and P. cocyta (as “Northern Crescent”) can be differentiated by the extent of orange on the dorsal hindwing.  I found this to be unreliable.  While univoltine P. cocyta does, in all cases,  have reduced black postmedian maculations and a broader orange field on the hindwing, individuals of both P. tharos and bivoltine P. cocyta vary considerably in this character.  In fact, individuals of bivoltine P. cocyta generally have fully-developed hindwing maculations and appear identical to P. tharos.  Yet, some P. tharos have reduced hindwing maculations, showing an extensive field of orange.  Thus, one cannot rely on this character.

Another, also somewhat unreliable way to distinguish the species is by habitat.  P. tharos is essentially an open field species, using white aster species as their larval hostplants.  Bivoltine P. cocyta is essentially a forest species and has not been found in open habitats.  At George Thompson WMA in Fauquier County, VA, for example, P. tharos is common around Lake Thompson, on the dam and along the open trail on the north side.  They are showing wing wear at the time when bivoltine P. cocyta emerges inside the forest.  Bivoltine P. cocyta can be seen along the north side of the lake along the forest edge and likely use the woodland aster that grows along the uphill trail.  The two species segregate themselves.  Univoltine P. cocyta is more of a mystery.  I have been looking for these for many years from western Maryland to Bath County, VA and over on the WV side of Reddish Knob – without luck with but one sole exception, a female taken at Sleepy Creek WMA in Berkeley County, WV that laid eggs and produced giant adults, compared to the other two species.

The relationship of the two P. cocyta species should resolve itself in coming months or a year or two.

The notion that there are species or subspecies hidden in our Maryland Phyciodes complex is one that we as diligent field observers can do a lot to elucidate.  Take careful photographs, making sure you have a male and can clearly see the underside of the antenna.  Net them if you need to. And make even more careful notes about the date seen, the behavior, the habitat, and the size of the population you encounter.  And include that data when you post your picture to Flickr, or iNat, or eButterfly, or the Maryland Biodiversity Project.

If you see something, say something!

2018 May 25_MD-Indian Springs WMA_Indian Springs Pond copy

Here’s the money shot you need — straight on, looking at the full underside of the antennal club on a male Phyciodes crescent. You don’t see many views like these on iNat [2018MAY25, Indian Springs WMA, photo by REB]

This entry was posted in conservation, evolution, general butterfly news, Identification tips, maryland, sightings, state butterflies, taxonomy and tagged , . Bookmark the permalink.

1 Response to A Tale of Two (or More) Crescents

  1. Jeff Cagle says:

    Thanks for the ongoing work!

    Two questions for Harry (or anyone who knows):

    (1) Scott in various publications made something of the antennal club shape – elongated in cocyta, more ovate in tharos. Does that hold up in your field work?

    (2) You mention that the univoltine cocyta flies in the high mountains – but also not in MD, WV, or VA. Does that leave NC, or could it also include points further north into northern PA, NY, etc?

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