How can one tell the difference between Antheraea polyphemus and Antheraea oculea as larvae when the ranges of the two species overlap?
You can’t, at least not reliably. Not because differences don’t exist (they sort of do – A. oculea tends to have a more heavily marked larva, with more strongly developed silver scoli, yellow oblique stripes, and setae), but because they don’t mean much when:
- it’s likely that the full range of variation in these markings overlaps between the two species and
- the Antheraea oculea/polyphemus complex is one of the many headache situations where the phenotypes are geographically clinal; it’s not clear where one’s range ends and the other’s start based on their phenotypes alone. For example, the polyphemus on the east coast look pretty different than most oculea, but the ones from New Mexico, Colorado, or Utah, etc. look virtually identical to oculea to me (i.e. geographically proximal and sympatric populations of oculea and polyphemus are more similar to each other than geographically distant populations within the latter species itself).
That being said, I think the current oculea/polyphemus IDs on iNat are mostly based on geography rather than phenotype, and thus there may be some erroneous circular data being generated – I doubt all the oculea/polyphemus IDs from New Mexico, southwestern Texas, and Mexico (the apparent areas of “sympatry” based on iNat’s range maps) are correct.
Thank you for your thorough answer!
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