This week we will test your butterfly ecology and your butterfly ID skills!
Which of the species below are you most likely to find in the habitat on the left?
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This was a difficult two-parter this week and results were evenly divided!
The answer is the bottom butterfly, the Bog Elfin!
Habitat: Most of the trees in this habitat are dwarfed evergreens, the few taller trees have sparse needles and the white poles of dead trees are prominent across the habitat. These features all indicate a bog. The spindly, thin shape of the taller trees indicate black spruce.
Who feeds exclusively on Black Spruce? It’s the elusive Bog Elfin! Bog Elfin are the smallest of our Vermont Elfins (Callophrys) ranging from 2.2 to 2.4 cm - about the size of a nickel. The top picture is the closely related look-alike, the Eastern Pine Elfin. Eastern Pine Elfins are marginally bigger than Bog Elfins at 2.5 - 3.2 cm - closer to the size of a slice of banana - and much more common.
In A Swift Guide to Butterflies of North America, Jeffrey Glassberg says of Bog Elfins, “If you are willing to travel to remote black spruce bogs and feed ravenous mosquitoes and black flies, you’ll have a chance of missing this mysterious butterfly yet again.”
Identification:
Both Bog Elfins and Eastern Pine Elfins can be identified from the underside of their wings, which is visible when their wings are folded. Bog Elfins have a more obscured pattern on their hindwing and are darker in color compared to the more dramatic pinks, whites, maroons and dark browns on the Eastern Pine Elfin.
The forewing of the Eastern Pine Elfin has a more disjointed PM line (A-left) and the Bog Elfin (A-right). The Eastern Pine Elfin hindwing has a submarginal grey band (B-left) outside a row of black crescents (D-left) while on the Bog Elfin the outer margin of their hindwing is frosted in grey (B-right) with less defined black (C-right). The Eastern Pine Elfin has maroon bars topped with pink bars on their hindwing margin (D-left) which is missing on the Bog Elfin.
Bog Elfins fly lower to the ground than Eastern Pine Elfins. Bog Elfins have one short flight period in late May/early June before they spend the majority of the year as a pupa. Eastern Pine Elfin can be seen over a longer time period from the end of April to the end of July. In Vermont, the Eastern Pine Elfin primarily utilizes the Eastern White Pine and Jack Pine as their host plants, although they are noted to use Black Spruce in Maine.
Bog Elfin by Naomi Cappuccino (iNaturalist)
Eastern Pine Elfin by Jeff Cherry (iNaturalist)
Black Spruce swamp by Kent McFarland (iNaturalist)
Ready for this weeks’ quiz? Click here for week 4’s quiz on sexing butterflies!
