BUTTERFLIES AND MOTHS
(Lepidoptera)
J.D. Lafontaine
DISTRIBUTION PATTERNS
This analysis of distribution patterns of Lepidoptera of the Mixedwood Plains Ecozone relies heavily on the distributional data from butterflies but other examples are included from the moths. For reference, a check list of the butterflies of the Mixedwood Plains Ecozone with distribution summary for each species is included in Table 3.
LEPIDOPTERA VAGRANTS \ MIGRANTS
About 100 species of Lepidoptera occur in the Ecozone as vagrants. Some of these are southern species that occasionally wander north into southern Canada while other species regularly migrate northwards each year and breed regularly in northern United States and southern Canada. The most famous of the latter group is the Monarch (Danaus plexippus) (Fig. LEP-8) but two butterflies, the Painted Lady (Vanessa cardui) and the Question Mark (Polygonia interrogationis) are also conspicuous seasonal components of the fauna. Some butterflies such as the Little Sulphur (Eurema lisa) and the Buckeye (Junonia coenia) (Fig. LEP-9) vary greatly from year to year in range and abundance.
Of the 30 species of vagrant butterflies 20 are very rare southern strays which rarely if ever breed in Canada. Most of these have been recorded only in the Carolinian Zone (zone 135) of southern Ontario. Of the remaining ten species of breeding vagrants, five occur widely over the Ecozone, two are restricted to southern Ontario and three occur widely in eastern Canada. The 30 butterfly vagrants represent 21% of the butterfly fauna of the ecozone, this reflecting the fact that butterflies tend to be powerful fliers. Another group of powerful fliers, the Sphinx Moths (Sphingidae), include 9 species (21% of the sphingid fauna of the ecozone) that occur in the Ecozone as vagrants. Two other families of Lepidoptera show a fairly high proportion of vagrant species: the Noctuidae (34 species; 5% of the noctuid fauna) and Pyralidae (14 species; 5% of the pyralid fauna). Among pest species of Noctuidae that migrate regularly into Canada are the Corn Earworm (Helicoverpa zea), Variegated Cutworm (Peridroma saucia), Black Cutworm (Agrotis ipsilon), and Fall Armyworm (Spodoptera frugiperda). Among the Pyralidae, two pests species are migrants: the Alfalfa Webworm (Loxostege cereralis) and Beet Webworm (Loxostege sticticalis). The former occurs in the Ecozone only in the summer but the Beet Webworm has become established in the northeast. Only a few species of microlepidoptera other than Pyralidae are migratory, the most famous one being the Diamond-back Moth (Plutella xylostella) which sometimes migrates in huge swarms numbering many millions of moths and has even reached Greenland (Wolff, 1964). Orthonama obstipata is one of the few vagrant geometridae that occurs in Canada; the species is worldwide in distribution but dies out over the winter in the northern part of its range and reinvades these areas in the summer. Ferguson et al. (1991), in a review of the Lepidoptera of Bermuda, lists 113 species of migratory Lepidoptera of the East Coast of the United States; 81 (72%) of these are known from the Mixedwood Plains Ecozone.
SOUTHERN LEPIDOPTERA
Species of Lepidoptera with a primarily southern range are arranged in three categories for discussion: those that occur north only into the Carolinian Zone (subzone 135) of southern Ontario; those that occur north through most or all of the Ecozone; and those that range well north of the Ecozone.
There are 18 species of butterflies, 12% of the butterfly fauna of the Ecozone, that reach the northern limits of their range in the Carolinian zone of southern Ontario. A small portion of this southern fauna, including some butterflies, e.g. Delaware Skipper (Anatrytone logan), Eastern Tiger Swallowtail (Papilio glaucus), extends into extreme southeastern Ontario and southernmost Quebec. In relatively well collected groups of moths the proportions of resident species restricted to the Carolinian zone vary greatly: Sphingidae, 2/42 (5%); Saturniidae, 4/16 (25%), Arctiidae, 9/56 (16%); Noctuidae, Catocala, 14/43 (33%). The unusually high percentage of Carolinian species of Underwing Moths (Catocala) is due to the large number of species (14) that are restricted to Hickory (Carya) as a larval food plant; most of the Carolinian species belong to this group of Hickory feeders. The low proportion in the Sphingidae probably represents the powerful flying ability and tendency of Sphinx moths to stray that results in their appearance in other parts of the Ecozone. Some Carolinian zone species in Canada are not widely distributed in the zone but are restricted to specific areas within the zone. For example, the Scalloped Sootywing (Staphyllus hayhursti) is largely confined to Pelee Island and only occasionally occurs at Pt. Pelee; the Frosted Elfin (Callophrys irus) (Fig. LEP-10) was confined to the areas of Lupine in the St. Williams area south of Simcoe; it is apparently extirpated from Canada. Duke's Skipper (Euphyes dukesi) is restricted to the extreme southwest corner of Ontario (Essex, Kent and Lambton Counties); the Dusted Skipper (Atrytonopsis hianna) occurs only in the area around Pinery Provincial Park.
There are 21 species of butterflies with distributions that fairly closely match the limits of the Ecozone. Exceptions to ranges that matches the Ecozone is that the ranges of many species (16/21) extend into the Muskoka area of Ontario and the ranges of only half of the species (11/21) extend down the St. Lawrence River to Quebec City.
A total of 30 species that are widely distributed in eastern United States occur north into central Canada well north of the Ecozone.
NORTHERN LEPIDOPTERA
Species of butterflies with primarily northern distributions are arranged in two groups: those that reach their southern limits within the Ecozone (23 species) and those that extend into eastern United States well south of the Ecozone (8 species). Almost all of the butterflies that reach the southern limit of their distribution in the Ecozone (19/23) occur as far south as the northern limit of the Carolinian zone (i.e. the boundary between subzones 134 and 135). Two boreal species occur as far south as the St. Lawrence River area, i.e. Common Branded Skipper (Hesperia comma and Bog Fritillary (Boloria eunomia) and two others reach their southern limit in southern Ontario, i.e. Common Ringlet (Coenonympha inornata) and Bog Copper (Lycaena epixanthe) (Fig. LEP-11).
PRAIRIE DISJUNCTS
Five species of butterflies and about 30 species of moths are prairie associates and reach the eastern limits of their range in the Ecozone. Two of the butterflies, Large Marble (Euchloe ausonides) and Garita Skipper (Oarisma garita) occur in eastern Canada only in the Manitoulin Island area and a third, Olympia Marble (Euchloe olympia) (Fig. LEP-12) has recently expanded its range from this area into western Quebec. The other two species, Karner Blue (Lycaeides melissa) and Gorgone Checkerspot (Chlosyna gorgone) were considered to be extirpated from Ontario. Surprisingly, five colonies of the Gorgone Checkerspot were discovered in Eastern Ontario between Kemptville and Prescott in the spring of 1996.
EASTERN SPECIES
The only butterfly in the Ecozone that has a distribution in the eastern Canada and reaches its western limits in the Ecozone is the Bog Elfin (Callophrys lanoriaensis) which occurs from Maine and Nova Scotia westward into the western Quebec (Lanoraie Bog) and eastern Ontario (Alfred Bog).