Junonia stemosa, commonly known as the twintip buckeye, is a butterfly species in the family Nymphalidae. It was described in 2020 and is found in southern Texas, particularly on barrier islands such as South Padre Island. Its larval host plant is Stemodia tomentosa (woolly stemodia), a light gray perennial common in sandy coastal soils. J. stemosa is closely related to Junonia coenia (the common buckeye) but can be distinguished by its unique morphological and ecological adaptations that allow it to feed on S. tomentosa.[2]
Junonia stemosa was formally described in 2020 as part of a genomic revision of North American Junonia butterflies.[2] The species was identified as genetically and morphologically distinct from both Junonia coenia (the common buckeye) and Junonia nigrosuffusa (the dark buckeye).[2] Analyses showed that populations feeding on Stemodia tomentosa in southern Texas represented a separate evolutionary lineage within the genus Junonia.[2] These findings supported the recognition of J. stemosa as a distinct species within the family Nymphalidae and tribe Junoniini.[2]
The species is endemic to southern Texas, particularly near the Gulf Coast, and its divergence is thought to have been influenced by host-plant specialization and geographic isolation from other North American Junonia species.[2]
Morphology
Adults of Junonia stemosa resemble Junonia coenia but differ by a more angular and slightly elongated forewing tip.[2] The dorsal surface is generally darker, with reduced orange patterning relative to J. coenia.[2] The species’ common name, the Twintip Buckeye, refers to the subtle twin-pointed shape of the forewing apex that is unique among North American Junonia.[2]
Freshly emerged individuals sometimes display a faint purplish or bluish sheen on the forewings.[3] The ventral surfaces are variable in tone but usually show muted brown or gray coloration with clearly defined eyespots that provide predator deterrence.[3] These morphological traits, combined with genomic evidence, support the species’ recognition as distinct from Junonia coenia and Junonia nigrosuffusa.[2]
Habitat and caterpillar foodplants of Junonia. U.S.A.: Texas: (a–c) Grey-woolly twintip (Stemodia tomentosa), foodplant of J. stemosa sp.n., Cameron Co., South Padre Island, N end of the city, E of SH100, 26.15501, -97.17254, 26-Dec-2015.
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