Know your butterfly species (or at least these 4)

Starting in mid-April this year, we began to see a few species of early-flying butterflies. In general, Juneau is not blessed with a great diversity of butterflies, for whatever historical and geographic reasons. I also suspect that butterflies in Southeast Alaska have not been as well studied as those in the Interior or, certainly, in the Lower 48. In any case, it was a treat to see these four kinds of early fliers in April.

 

Milbert’s tortoiseshell

Arguably the most colorful of the early fliers, this butterfly has broad orange bands on the upper surface of the spread wings and some red spots at the leading edge of the forewing. On some individuals, however, the orange and red marks are not bright. The undersides of the wings are brownish and much less conspicuous. Males and females are similar. This species overwinters as adults, tucked into crevices of tree bark and buildings. After emergence from hibernation, females lay eggs, which produce a new generation of adults in summer. The larvae feed on stinging nettles, good stands of which are found here in several locations.

Adults like to bask in the sun as they perch on branches, grass or the ground. They visit flowers for nectar and can serve as pollinators by carrying pollen from one flower to another. We saw this species visiting the ornamental coltsfoot the Jensen-Olson Arboretum in mid-April.

Mourning cloak

This is another beautiful butterfly that overwinters as an adult. The upper surface of the wing is dark, rich brown, bordered by a wide yellow band on the wing margins. Males and females are similar. A favorite larval food in Alaska is willow leaves, but other hosts are included in the diet elsewhere (and perhaps also in Alaska).

Adults often bask in the sun as they perch. They can be seen visiting the sap wells that sapsuckers carve on willows and other trees, and they also feed on animal dung and decaying organic material. They may occasionally go nectaring and serve as pollinators.

Blues

There are several species of small bluish butterflies in Alaska, and I don’t know which one(s) we have here. Although the “Butterflies of Alaska” by Philip and Ferris indicates that blues usually emerge and fly in late May or June, at the earliest, in late April this year, hikers were treated to a small, bright blue butterfly flitting along the trail. When it perched with folded wings, the brownish undersides of the wings made it nearly invisible; upon take-off, the brilliant blue was again exposed. This was a male; the females lack the bright blue and are more camouflaged in mottled brownish-gray.

Some blues hibernate as pupae, on the way to transforming from larva to adult, but some pass the winter in the egg stage. Host plants for larvae are varied, and for some species, unknown for Alaska. Eggs are commonly laid in flowers, and the larvae eat the flowers or, in some cases, seed pods of the host.

Blues belong to a taxonomic family (Lycaenidae) in which a number of species are well-known to be part of an interesting symbiosis that may occur in Alaskan species too. The larvae are tended by ants, which guard them against would-be predators. The ants benefit by feeding on excretions from the larval digestive tracts. Juneau, however, does not seem to be home to many ants — I see them only in a few places — and therefore it is uncertain if this symbiosis occurs here.

Whites

Bigger than blues, but smaller than mourning cloaks and tortoiseshells, they come in a range of whitish-ivory-pale yellow hues. Females are duskier than males. Our whites are currently classified as margined whites; taxonomists call it a “species complex,” meaning that they are not sure how many, or which, species are here. I saw several in late April, earlier than the dates given in “Butterflies of Alaska.”

The larval host plants are plants of the mustard family. They are presumed to overwinter as pupae. Adults visit many flowers and can be effective pollinators.

All of these species exhibit a particular behavior called “puddling.” Butterflies of many species visit moist soil, decaying material, and places where an animal has urinated, sometimes gathering in large, spectacular aggregations. In most cases, these are males. For some species, the big attraction is salt, specifically sodium; for others, it is nitrogen. At least in some species, males can transfer the nutrients to females at the time of mating, and this leads to better reproductive success, but we have no information on this from Alaskan species.

As summer comes, there will be more butterflies to see, some of them residents, some of them vagrants. Climate warming is likely to permit more species to visit or live here — more fun for butterfly watchers.


• Mary F. Willson is a retired professor of ecology.


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