With warmer weather right around the corner, we’ll undoubtedly start seeing some insect activity in the coming weeks. So dust off your bug ID brain and have your camera ready because What’s Buzzin’ will follow suit in no time!
This week, we’ve compiled a quick identification guide to help you ID some of Montana’s early fliers.
Important Terms
If you’re out in the field, using a physical key to identify butterflies can be especially challenging if you’re unfamiliar with many of the terms. Postmedian band, marginal band, subapical, basal area – these are all terms used to describe areas of a butterfly wing. Nothing is more frustrating than watching a small, flying critter and trying to remember what part of the wing is the dorsal submarginal band and, good God, where the heck is the ventral discal area? My favorite guide to identifying these easily-mixed-up areas of the wings is from Northwest Butterflies, which provides an overview of basic terms and visual guides to the various medians and margins of a butterfly wing.
Commas (Polygonia sp.)
Glenn, our resident native butterfly expert and Development Director, put together a quick and easy dichotomous key to differentiating between the four species of commas in western Montana. Commas, like many of our early spring butterflies, overwinter as adults and emerge at the onset of spring to mate and lay eggs. Their name comes from a white, comma-shaped spot on the underside of their wings.
1. Does it have a “double spot” in the center of the forewing (green circle)?
a. No – It’s likely a hoary comma (Polygonia gracilis – larvae feed on currants and gooseberries)
b. Yes – Go to step 2
2. Does it have a thick, dark border with small yellowish spots in the hindwing border?
a. Yes – It’s likely a green comma (Polygonia faunus – larvae feed on willow and birch)
b. No – Go to step 3
3. Does it have a light, orange-yellow wing margin and a black, triangular spot in the center of the hindwing (blue circle)?
a. Yes – It’s likely a satyr comma (Polygonia satyrus – larvae feed on nettle)
b. No – It’s likely an oreas comma (Polygonia oreas – larvae feed on currants and gooseberries)
Tortoiseshells (Nymphalis sp. & Aglais sp.)
Mourning Cloak (Nymphalis antiopa)
Montana’s state butterfly is unmistakable, cloaked in dark brown with striking yellow trim and blue spots bordering the wing margins. Nymphalis antiopa, the mourning cloak butterfly, feeds primarily on tree sap and is commonly seen in wooded areas, but it is no stranger to urban parks and suburbs. The mourning cloak’s wing pattern is entirely unique, making it easily recognizable, even in flight. Larvae prefer feeding on willow but will eat other deciduous shrubs and trees.
California Tortoiseshell (Nymphalis californica)
The California tortoiseshell might be mistaken for a comma at a distance; the bright orange wings with black margins and simple black spot pattern are reminiscent of the comma’s wing patterns. However, tortoiseshells are larger, and the underside of the wing lacks the classic “comma” shape that gives commas their name. The hindwings mostly lack spots, except for a single black spot near the top wing margin that is sometimes hidden by the forewings. Caterpillars feed on buckthorns in the Ceanothus genus.
Compton Tortoiseshell (Nymphalis l-album)
The Compton tortoiseshell is another orange-and-black butterfly that could be mistaken for a comma at a distance, but like the California tortoiseshell, it is larger than the commas and lacks the white comma mark on the underside of the wings. For a confident ID, look for the white spot on the hindwing. Larvae feed on willow and birch.
Milbert’s Tortoiseshell (Aglais milberti)
The Milbert’s is pretty hard to misidentify – after all, not many butterflies stare back at you. The unmistakable eyes on the upper forewing stand out against the dark brown background, with a thick, bright orange submarginal band that fades to a pale yellow postmedian band. Larvae feed on nettles.
We have some warm weather in the forecast, so get out there and see if any of these early-season fliers are out and taking advantage of it. Don’t forget to submit your pictures to bugid@missoulabutterflyhouse.