A female western tiger swallowtail (Papilio rutulus) eclosed; stock originated from a single pairing between reared female and wild male in Albany, California, Summer 2017. We also captured a female eastern tiger swallowtail (Papilio glaucus) at Cornell Botanic Garden. This post makes a basic comparison between these two representatives of their respective species.
Today, we had a medium sized Papilio rutulus female eclose from pupae originating from Albany, California. We also happened to catch a Papilio glaucus female at at the Cornell Botanic Garden. This is the first time we have had live specimen of the two similar species side by side, so we took this as an easy opportunity to compare them. Additionally, since the geographic range of both these species is quite vast and significant regional variation in phenotype is expected, this comparison may offer insight for the California Bay Area and Upstate New York type localities.
Below, the rutulus female is shown to the left, the glaucus female in the middle, and the two species side by side to the right.
Granted, the glaucus female has been free to rome the wild for a while and therefore not as pristine as the rutulus, it does seem that the glaucus is a paler shade of yellow with much more pronounced win venation. The rutulus is a deep, rich shade of yellow, creating an overall yellower appearance, similar to another western species, P. multicaudata. Although the venation is less pronounced in the rutulus, as well as some of the internal black stripe patterning, the black bordering the wings seems to be thicker proportional to the total wing area. Like the other rutulus females we have seen, there is a slightly visible yellow stripe running between the black border of the forewing, which contributes to making the black appear thicker. These elements make the rutulus appear "cleaner".
Interestingly, neither of the pictured individuals have much blue. This is interesting, at least for the glaucus, since glaucus females are known to have more blue coloration than other "tiger" species, with one hypothesis for this being that the dark form evolved to have more blue coloration to be better mimics of Battus philenor and that the yellow form retains this trait (reference). The dark form does not seem to be common in Ithaca and B. philenor is not present here. Additionally, the pictured female is quite small and small individuals tend to have less blue coloration proportional to total wing area, perhaps because blue is a costly color to produce and small size correlates with poor larval diet. Similarly, the rutulus female is smaller than the other females that eclosed this year from the same progeny and these other females have a bit more blue. Another thought is that the glaucus in Upstate New York are similar to P. canadensis, which is smaller than glaucus and lacks extensive blue coloration. They fly sympatric to glaucus in some parts of this region and likely hybridize, but probably not here in Ithaca.
A point to make is that the glaucus has more of an orange coloration at the base of the hindwings rather than a reddish color, and the uppermost discal spot is orange rather than yellow. This orange spot is present in other eastern species like P. troilus and P. polyxenes but not in any of the western species that we know of. The role of this spot is unclear, especially because the area of the wing that it takes place is usually covered by the forewing when the butterfly is at rest. One possibility could be to mimic B. philenor (troilus and polyxenes are mimics, too), which has similar orange spots on its hindwings; however, these spots are limited to the underside of the hindwing and the mimicking species do also have orange coloration on the underside of their hindwings.
One last thing to note is that the glaucus has an overall much more convex wing shape whereas the rutulus is more concave. Both the forewings and hindwings of the glaucus are shorter, rounder, and less sharp at the ends. Although the swallowtail tail area of the glaucus are a bit torn, it does seem as though that the tails are also shorter than the rutulus's. These features make the rutulus appear more triangular. In addition, the chain of yellow spots along the wings are rounder in the glaucus, although both species likely can have both extremes of this trait.
Brian Liang is a student at Cornell University in Ithaca, New York pursuing an undergraduate degree in entomology. He is co-owner and a main contributor of the Liang Insects blog, insects articles, and site design.
Ithaca, New York
This timeline is a series of daily posts recording our observations and experiences with various insects (primarily Lepidoptera) around the Cornell University campus in Ithaca, New York, starting from the time we moved here in 2017. As this is a personal blog, we try to keep collections/rearings for university research and course work to a minimum, and mainly focus on just the species we catch and raise for our own fun and interest. Posts prior to this time can be viewed at Timeline 2012-2017: Albany, California, though there is occasionally some crossover when we have returned home during breaks or reared stock derived from home (see Albany, California Updates).
July 2020 (1)
August 2019 (2)
July 2019 (35)
June 2019 (46)
May 2019 (20)
March 2019 (1)
January 2019 (1)
September 2018 (1)*
August 2018 (9)*
July 2018 (11)*
June 2018 (22*)
May 2018 (18)*
April 2018 (2)*
January 2018 (6)
December 2017 (5)
November 2017 (1)
October 2017 (5)
September 2017 (26)
August 2017 (19)
*Currently, a significant portion of 2018 posts are missing. The notes/photos for this time period are saved on our personal files but the posts were never built due to a busy schedule that year. We are still actively building these posts when we have the time.
Full Species List
(Alphabetical by scientific name)
- Not every species we encounter is necessarily presented on this site, rather a selection of those that were of particular interest to us and that we felt were worth documenting.
- We can't guarantee that all species have been identified accurately, particularly taxa we are not as familiar with.
Battus philenor hirsuta
Liminitis arthemis arthemis
Limenitis arthemis astyanax
Papilio polyxenes asterius
Papilio polyxenes asterius × Papilio zelicaon
Albany, California Updates