The Asterocampa Enigma: Empress Leilia in central Texas
Long story short: Empress Leilia is common throughout central Texas and many of them are mis-identified as Hackberry Emperors on iNat. Confirmed today on BAMONA: https://www.butterfliesandmoths.org/sighting_details/1140662
Tagging the top 5 Hackberry Emperor identifiers in Texas to notify! @greglasley @maractwin @nlblock @aguilita @sambiology
Short story long: I've been raising a million Tawny Emperors (have you noticed?), and have also raised Hackberry Emperors enough to easily distinguish the two from a zoomed out blurry photograph. However, my world has been shaken: I thought these were the only two species in Central Texas, and have had all my Hackberry Emperor observations verified to research grade, etc. etc.
As I raised tawny emperors, I noticed that the Key Feature often used to distinguish them from hackberry emperors (the intact vs broken basal discal bar) is not a reliable feature--I have not yet tallied up the numbers, but my estimates are that around 25% of the butterflies I have released have had the broken bar. Basically, you have to use the forewing eyespots to tell them apart--hackberry emperors have them, tawny emperors do not. So already I am realizing that there is still some uncertainty in identification of these fairly similar species.
I recently found another hackberry emperor caterpillar (they are easily distinguished from tawny emperors by the horns shape), but something seemed off about it. I'm used to the mostly black, streaked with white faces I've seen in hackberry emperors. This one has a green face with brown horns. I've only seen one photo of a caterpillar that looked like that, and it was an Empress Leilia, which I thought we did not have here. I dug in a little further, and by a little further I mean I downloaded and skimmed through the 1987 genus revision by Timothy Friedlander (http://lepidopteraresearchfoundation.org/journals/25/PDF25/25-215.pdf).
Here's the deal:
Hackberry Emperors: broken basal discal bar on forewing, one black eyespot on the forewing (when opened), two cells separating eyespots on forewing (when closed)
Empress Leilia: intact basal discal bar on forewing, two black eyespots on open forewing, median white spots, and one cell separating eyespots on closed forewing.
I have been seeing Empress Leilias frequently throughout the year, but they have all been identified as Hackberry Emperors (they are closely related). One thing that bothers me a little: I found a cluster of three eggs, which I raised and released. All three hatched at the same time, but two matured and flew off a few days before the third. Photos of the first two show hackberry emperors. The third is an Empress Leilia. I also have observations of a number of butterflies who show a combination of characteristics of both hackberry emperor and empress leilia... Not really sure how to categorize those but it seems important to mention!
Hackberry emperor by eyespots, Empress leilia by basal discal bar
Empress leilia by eyespots, Hackberry emperor by basal discal bar
Comentarios
I am aware that Empress Leilia is in central Texas, and have posted several of them already. I always try to consider all three Asterocampa species when identifying these. Which isn't to say I haven't made mistakes with these...
The southwestern subspecies Hackberry Emperor (i.e., the one that overlaps with Empress Leilia mostly) has forewing eyespots that are virtually identical to Leilia: http://butterfliesofamerica.com/L/t/Asterocampa_celtis_antonia_a.htm. I'm not sure if they can be useful in telling the two species apart dorsally, but there might be differences in the internal color of the eyespots ventrally. Some H. c. antonia (and probably the other two subspecies) can have an unbroken basal discar bar, but it is still always quite jagged in shape, as far as I know. I don't know that Empress Leilia ever shows a very jagged shape to this bar. There is also a basal bar on the ventral hindwing that is usually broken in Hackberry but unbroken in Leilia.
You're in an area where I think there's some bleeding of traits between a couple Hackberry subspecies, which is why you might sometimes get individuals with only a single forewing eyespot (or it could be because of hybridization between Tawny and Hackberry...who knows!). I suspect that these three species can all hybridize, but I don't know for sure.
I would be very suspect of a cluster of eggs being the result of multiple females laying them, unless you actually saw it happen. I think it's more likely that the differences observed are the result of variation within the population.
I've got two of what I'm calling Hackberry emperor:
http://www.inaturalist.org/observations/6744737
http://www.inaturalist.org/observations/6325971
They look good for Asterocampa celtis antonia compared to images I'm seeing on BugGuide, but they do have similar forewing eyespots to leilia.
Thank you all for the comments! It's so hard to get good authoritative information online, especially on heavily citizen science based sites. The revision goes in depth into crossbreeding attempts and I need to read the whole paper closely, but my skimming seemed to say that hackberry and tawny emperor don't hybridize (or at least they didn't back then!). I wish I knew more about the mechnanism of wing pattern formation--I tend to assume structual/morphological features are more reliable than pattern and coloration which tends to vary, but I don't know to what extent wing patterns are structural or coloration.
Añade un comentario