With the recent cold and new snow on the ground - we’re thinking of our overwintering adult butterflies - like the Commas.
Which of these butterflies in a Gray Comma?
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The butterfly on the right is the Gray Comma!
This week was looking at the upperside differences between the Gray Comma and the more common Eastern Comma. The key to tell apart these two related species are the number of spots on their hind wing. The Eastern Comma has three black spots arranged in a triangle on the hind wing, while the Gray Comma has only two black spots in this position. The Gray Comma also usually has a full line of yellow dots within the dark margin of the hindwing, whereas the yellow dots on the Eastern Comma typically don’t form a full line.
Like many Polygonia species, the Eastern Comma has a red form (pictured here) and a black form (mainly during the summer). The hindwing of a black form individual can obscure the third black spot making them harder to identify.
In the related Asian Comma, this switch between seasonal phenotypes - having different looks in different seasons - is triggered by length of day and sometimes tied to reproductive ability. Black form summer individuals are often ready to reproduce immediately after eclosing, while red form winter individuals often have to undergo hibernation first.
Nylin, S., 2013. Induction of diapause and seasonal morphs in butterflies and other insects: knowns, unknowns and the challenge of integration. Physiological Entomology, 38(2), pp.96-104.
Shapiro, A.M., 1976. Seasonal polyphenism. In Evolutionary Biology: Volume 9 (pp. 259-333). Boston, MA: Springer US.
Eastern Comma by wilderbombyx (iNaturalist)
Gray Comma by Allan Harris (iNaturalist)
The next quiz is another two parter - test your plant and butterfly ID knowledge here!