May I receive confirmation on the correct usage for Danaus plexippus ssp. plexippus vs. Danaus plexippus? Is the “Migratory Monarch” identification only for the last generation each year where that individual organism will be migrating? Or are all Monarchs (here in Wisconsin) considered “Migratory Monarchs” because they are part of that overall annual cycle of migration, even though several generations each year do not migrate? Thanks! :)
6 Likes
Welcome Kate! Great question. I don’t know the answer, but I’m waiting for the answer. I observed a monarch this morning, and someone used the migratory subspecies. I’ve never seen it before.
1 Like
this from wikipedia:
-
D. p. plexippus – nominate subspecies, described by Linnaeus in 1758, is the migratory subspecies known from most of North America.
-
D. p. p. “form nivosus”, the white monarch commonly found on Oahu, Hawaii, and rarely in other locations.
-
D. p. p. (as yet unnamed) – a color morph lacking some wing vein markings.
-
-
D. p. nigrippus (Richard Haensch, 1909) – South America - as forma: Danais [sic] archippus f. nigrippus. Hay-Roe et al. in 2007 identified this taxon as a subspecies[23]
-
D. p. megalippe (Jacob Hübner, [1826]) – nonmigratory subspecies, and is found from Florida and Georgia southwards, throughout the Caribbean and Central America to the Amazon River.
-
D. p. leucogyne (Arthur G. Butler, 1884) − St. Thomas
-
D. p. portoricensis Austin Hobart Clark, 1941 − Puerto Rico
-
D. p. tobagi Austin Hobart Clark, 1941 − Tobago
2 Likes
This sounds correct. I’m sure others could comment more about this specific case, but if it’s a subspecies then it would refer to all monarchs in a certain area regardless of generation.
3 Likes
United States Fish and Wildlife Service says there are two monarch butterfly populations in North America - eastern (east of the Rocky Mountains) and western (west of the Rocky Mountains). The eastern population overwinters in central Mexico and breeds throughout the United States and southern Canada. The western population overwinters along the California coast and breeds across the western states and southern Canada.
I believe this is what the name distinction is about.
2 Likes
Yes this is correct
1 Like
Thank you for this question, and the answers. I wondered this as well, when an identifier IDed one of my observations to ssp. plexippus.
But none of my other 60 observations (all in Eastern US) were ever IDed to ssp.
So, should I always identify them to ssp.? Or does it not really matter, since species is what really counts, and ssp. is implied by location?
I changed mine to reflect the change. I am still in the process of getting my mind changed to remembering it.
I think of it as fine tuning the names. I’ve also fine tuned my White-tailed Deer to Northern White-tailed Deer.
I am still learning about the differences between Red Spotted Admiral, Red Spotted Purple and White Admiral × Red-spotted Purple (Limenitis arthemis arthemis)
2 Likes
Thanks, all! I noticed a user recently this year IDing to the subspecies level, so I will save them the click and start using it myself. It’s been a really great year for monarchs (in my gardens)!
3 Likes
Ssp. shouldn’t be implied by location unless the sspp. were described based solely on location. Like species descriptions, ssp. descriptions must include a diagnosis, that is, what traits define the taxon as different from similar taxa.
A great question! I personally ID a lot of USA monarchs; people have been asking this (and similar questions) a lot. So forgive me if I overshare - perhaps this will be a good repository for answers to these questions!
The first thing to recognize, perhaps, is that Danaus plexippus (the species, aka Monarch) is absolutely correct - there’s nothing at all wrong with that ID! Danaus plexippus ssp. plexippus (the subspecies, aka Migratory Monarch) is just more specific.
In my opinion, whether to ID to subspecies (and not just with Monarchs) generally comes down to personal preference; some people like to, while others think the species ID is good enough.
Broadly speaking, there can be challenges with identifying to subspecies level. Sometimes taxonomy is outdated or incomplete; sometimes it’s impossible to track down useful reference material; sometimes one simply can’t figure subspecies based upon a mere photograph.
That’s not especially the case with North American Monarchs! iNaturalist generally recognizes two taxonomic authorities for North American butterflies: Pelham’s Catalogue, and Warren et al.'s Illustrated Lists. In the Catalogue (which covers the USA and Canada), there’s only one subspecies listed: Danaus plexippus spp. plexippus. In other words, the Catalogue says that’s the only subspecies in the USA and Canada. Meanwhile, the Illustrated Lists (which covers the Western Hemisphere), lists six subspecies, and provides geographic locations; again, Danaus plexippus ssp. plexippus is the only subspecies listed for the USA and Canada.
As an aside, for Canada in particular there’s another very helpful online taxonomic resource - Butterflies of Canada by Layberry et al. That source notes “There are several non-migratory subspecies in Central America, but only the nominate D. plexippus plexippus is found in North America and the rest of the world.”
More fundamentally, one thing to realize is that if a taxon has subspecies, then every specimen must fit into one of those subspecies or another - there aren’t free agents existing outside that taxonomic framework. 
If one digs into the literature, the overall Monarch subspecies situation is a bit more nuanced. The U.S. Fish and Wildlife Service’s December 2024 Species Status Report for the Monarch does a good job of outlining the current state of affairs. The general thinking is that perhaps there are fewer than the six subspecies listed in Warren et al., and perhaps it is not subspecies plexippus that resides in southern Florida.
But while there is some debate regarding the number of monarch subspecies and the extent of their respective geographic ranges, for everywhere in the USA and Canada (except Florida), our taxonomic authorities and recent research clearly point in one direction: there is only one subspecies: Danaus plexippus spp. plexippus (aka Migratory Monarch). Another aside here - a number of decades ago, some believed Western USA and Eastern USA monarchs represented distinct subspecies; that’s no longer the case.
That lands us back at identification preferences. On one hand, (1) why bother identifying USA/Canadian monarchs to subspecies if they’re all that subspecies? Versus (2) why not identify to subspecies if there’s no doubt that’s what it is?
Personally, I reckon if we have the taxonomy, we should try to use it - what’s the point of its existence otherwise? Further, since this is a website for submitting observations and identifying them, why not identify them as specifically as possible? And for example, if there’s only one species in a genus, should we not bother identifying to species, because it’s obvious? No, of course not! (Haha, how do you like my straw man?) At any rate, I certainly don’t begrudge anybody just identifying to species - that’s 100% cool in my book! And it’s awesome that we’ve recently seen improved notification settings for subspecies identifications - very helpful. One fun thing about subspecies identifications is that it often generates conversations like this one!
I know this post is getting long, but turning back specifically to the “migration” issue. Yep, all monarchs in the USA/Canada (except maybe Florida) are the same subspecies - regardless of what time of year a specific specimen is found. The English common name for subspecies plexippus (Migratory Monarch) can really be a bit of a misnomer - some populations (and certainly some specific specimens) don’t migrate! Another aside - yes, generally there is a long migration south in the fall by one generation, but those earlier generations are making incremental migrations north in the spring and summer, too!
@jasonhernandez74 is of course absolutely correct that generally there must be traits that define one taxon as different from another. With monarchs, various researchers have opinions about coloration, wing size, genetics, etc., for example, as means of distinguishing between subspecies. But since they all agree that the only subspecies found across Canada and the USA (except Florida) is subspecies plexippus, as a practical matter those various traits don’t necessarily matter too much for identification purposes here.
15 Likes
Really appreciate your thoughtful and thorough post here! I’m glad you’ve IDed many of my monarch observations and introduced me to this new topic. :)
1 Like
How would I recognize a vagrant Floridian or Central American Monarch if I wanted to look out for them out of their documented ranges? I think it’s not unreasonable to think that ones in Florida will get blown into other states occasionally, and iNat is well situated to document those types of occurrences.
5 Likes
These geographic assumptions may be good enough for our purposes on iNat, but they are not helpful for understanding what defines the subspecies. Surely taxonomic literature does not permit describing subspecies solely on where they are found.
For example: my go-to reference for Caribbean butterflies, Riley (1975), discusses the Monarch thusly:
The Bahamas and Cuba are populated by the migratory North American subspecies plexippus. In Hispaniola, Porto Rico, Jamaica, the Cayman Islands, and the Lesser Antilles, though with a good deal of overlapping, the sedentary subspecies megalippe Huebner 1819 replaces it. This has a less pointed forewing and much less heavily white-spotted borders, the veins, particularly of the male, are less heavily blackened, and the pale spots on the forewing immediately beyond the end of the cell are always small, often absent.
So that is four morphological differences. The two subspecies are not defined solely by geographic range. Now, in the case of the Monarch, there is that “good deal of overlapping”; but even in taxa where subspecies do not overlap, they are defined by differences besides where they are found. When I ID Caribbean butterflies, I will look at what island the observation was made on and whether that island has its own subspecies, but if I can’t see the described differences that define that subspecies, I’m still going only to the species level even if the island in question has only the one subspecies.
4 Likes
Oh, I agree with your taxonomic take! There are described morphological differences, and it’s good to learn them! It’s just that if one is identifying a monarch in Wisconsin or California or New England to subspecies level, for example, there’s not much need to necessarily pay much attention to how it’s distinguished from a subspecies that’s never been documented within 1,000+ miles of the region. It’s not any different from taxonomic identifications at any other level; for example, if there’s a too-blurry photo of what’s nevertheless clearly a giant swallowtail of some sort (genus) in California, it’s getting identified as a Western Giant Swallowtail (species) - because nobody’s ever found the alternative (but physically quite similar) giant swallowtail species within hundreds and hundreds of miles. If anyone ever does find one, obviously, that could change the calculus. Not adequate for rigorous taxonomic studies, but more than reasonable for iNaturalist identification purposes - or not a deviation from common iNat practice, anyway.
3 Likes
It’s used if it is in that subspecies. Very simple.
Thanks for such a good, thorough explanation! I actually saw this post as I was looking through the forums and thought of you since I’ve seen you on a bunch of monarch observations ID’ing them as this subspecies. And lo’ and behold, here you are!
1 Like
This topic was automatically closed 60 days after the last reply. New replies are no longer allowed.