|scientific name Nymphalis vau-album |
common name Compton Tortoiseshell
Found in or near moist mixed wood forests in the boreal and mountain region.
One brood per year, appearing in early spring (April to May) and again in August to October.
Somewhat similar to the California Tortoiseshell (Nymphalis californica), but the Conmpton has a predominantly pale hindwing margin (and is larger), while that of californica is black.
This is another species whose scientific name has received a complete makeover as a result of careful study by a number of researchers; the Compton Tortoiseshell was traditionally known as Nymphalis vau-album, but may be known as Roddia l-album in the future; it is more closely related to the commas (Polygonia) than members of the genus Nymphalis, and may represent an evolutionary linkage between these two groups (Nylin et al. 2001). For a complete review of the nomeclature changes, see Guppy & Shepard (2001).
Bird et al. (1995) call AB populations ssp. j-album, while Guppy & Shepard (2001) treat them as the western watsoni. Layberry et al. (1998) do not recognize watsoni as a sufficiently distinct taxon, presumably because of minor differences between the two, and treat all Canadian populations as j-album. A review of this situation is in order.
The light green eggs are cylindrical and have 11 vertical ridges. Mature larvae are black dorsally and brown laterally, with black, branched spines and fine white markings (Guppy & Shepard 2001). The pale green pupae have pinkish spots and three pairs of golden-silver spots on the back (Guppy & Shepard 2001). The adults emerge in late summer and hibernate, with mating and egg-laying occuring in the spring. This tortoiseshell has irruptive population dynamics, and may be very rare or absent many years in a row, then appear abundantly for a year or two. When it is common, it can be found during the winter in unheated, outdoor shelters such as barns and outhouses. In suitable years, possibly when outbreaks occur, this species will also migrate beyond its normal breeding grounds.
Not of concern.
In British Columbia, the only recorded larval hostplants are birches (Betula spp.) (Guppy & Shepard 2001). Adults prefer tree sap flows and mammal scat to flowers, and in outbreak years can form large mud-puddling congregations.
This species spans two continents, occuring across northern North America and also in Eurasia. It is found throughout most of non-arctic Canada and the northern United States (Opler 1999). May be a migrant to the northern- and southermost extents of its range; Opler (1999) depicts the northern Alberta records as migrants, but the Compton is found regularly there and there is no reason to believe these individuals represent migrants.
Joe Belicek (2014-03-02)
The name Papilio vaualbum Schiffermueller, 1775, is a nomen nudum, and as such it is unavailable for the purposes of zoological nomenclature as per Code. The new name Papilio l-album was introduced by Esper, in 1781. Currently, this species is placed in the genus Roddia Korshunov, 1995, as Roddia j-album (Boisduval & Le Conte, . Based on barcoding, the North American species is genetically distinct from the Eurasian Roddia l-album (Esper, 1781).
Joe Belicek (2014-03-03)
The geographic range of Roddia j-album in North America is decidedly northern, boreal & montane. Specimens have been collected in Alaska, in all Canadian provinces & territories (including Newfoundland & Labrador), & the northern tier of the US states. I have seen specimens from most of its range. As a robust insect, & strong flier, extralimital stray specimens have been recorded far away from its normal range, ? most likely carried there by strong winds. However, there is no evidence that it is habitually a migratory species.
Affiliation. This species is a member of Anglewing butterflies, (clade Papiliones angulati sensu Schiffermueller, 1775), which are undoubtedly a monophyletic group, as evidenced by the shared, apomorphic (unique) characteristic, i.e. the cryptically coloured and patterned ventral side of their wings. The resulting camouflage provides the hibernating butterflies a great degree of concealment against predators (i. e. small rodents). The group consists of seven, closely related, but distinct lineages, namely genera: Inachis, Aglais, Euvanessa , Nymphalis, Roddia, Polygonia & Kaniska. Depending on the point of view, the group is also known as Nymphalis sensu lato.
Voltinism & sexual dimorphism: confirmed as univoltine species from all observations to-date. Not only are the females of this species slightly larger than males, but the color & pattern of the ventral side is phenotypically distinct from males; not variegated but more uniform, suffused grey-brown.
Larval food plants: Canadian Forest Insect Survey recorded various species of birch trees (Betula sp.), Elms (Ulmus sp.), Poplars (Populus sp.). The record of Ash (Fraxinus sp.) is unverified from Massachusetts.
Joe Belicek (2014-05-10)
Adult feeding behaviour: in the early spring, after emerging from the overwintering shelters, the butterflies do not have many opportunities and resources where they can find nourishment. At this time, the only sources of sugar is the tree/shrub sap and willow catkins. The butterflies utilize both of these, the tree sap being the primary food source. The tree sap often oozes from the boreholes caused by birds (sap-sucker holes, or from bark injuries however caused. This may include sap flowing from stumps after the trees were cut. Willow catkins are occasionally visited by all Anglewing butterflies, but the amount of nectar obtained from catkins is negligible, compared to free flowing sap. The new generation of these butterflies, emerging in late June, early July was occasionally seen on flowers of thistles. However, it is more likely that the butterflies were attracted by sugary exudate of aphids, commonly infesting tender terminal growth on thistles. I have seen Aphid exudate on other plants, (including Poplars), being utilized as a food source in late summer. Anglewing butterflies only seldom visit flowers. However, they do opportunistically. In 2011, I collected several specimens nectaring on flowers of Goldenrod (Solidago spp.), in northern British Columbia. The butterflies are sometimes attracted to animal scat, probably sought after as the non-nutrient diet supplement. In the fall, the butterflies imbibe the cocktail from fermenting fruit (apples, pears, etc.), which contains sugar, alcohols, glycols. This enables the butterflies to fortify the body fluids with a mixture of antifreeze. Thus acquired cold hardiness is essential for survival of the Anglewing butterflies over the winter moths, without freezing. Sugar-malt based baits/traps could be exploited in attracting these butterflies, particularly in the spring, when the food sources are scarce.
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