Wisconsin's Butterflies & Moths

Wisconsin's Lepidoptera, an order of insects that includes the butterflies, moths, and skippers, are a fascinating blend of species that include relic populations of arctic species in our northern bogs, prairie species approaching their easternmost geographic extent in our prairies, and even migratory species of subtropical origin. Although many species are widespread, often common, and tolerant of habitat disturbance, the majority are specialized to varying degrees, thriving only in the limited areas that satisfy their entire range of often very exacting ecological requirements.

Moths

Wisconsin's Lepidoptera fauna probably numbers well in excess of 2400 species. The vast majority of these species are moths, which have not received the attention that butterflies have due to the greater difficulty encountered in observing and identifying these predominately night-flying insects. The thirteen moth families loosely referrred to as the macrolepidoptera are reasonably well known, with 1224 species documented in Wisconsin. The remaining moth families, the microlepidoptera, are very poorly known, with likely more than 1200 species occurring (an estimate since no comprehensive state checklist has yet been compiled).

Butterflies

The butterflies are the most colorful, visible, and popular of Wisconsin's Lepidoptera, with 155 species recorded in all. Of these, 118 are permanent breeding residents. Twenty-two are considered strays, far out of their normal geographic range and included in our fauna often on the basis of a single incidence. The other 15 species may be classified as migrants. They usually are unable to survive cold northern winters but periodically disperse into Wisconsin from their overwintering range in the south. The monarch is the best known example of this latter group and is present every year. Most of the other migratory species appear irregularly in Wisconsin, often not being seen for several years. Early season arrivals may locate suitable host plants and breed, building up local populations by late summer.

Lepidoptera Status

Since the bulk of our knowledge of occurrence and distribution of Wisconsin's Lepidoptera has been gathered within the last few decades, a reliable baseline by which to measure long-term decline is lacking. Rare species continue to be found as unstudied areas are surveyed. However, loss of native vegetation such as the nearly total conversion of prairie to agriculture has obviously taken a considerable toll. Our rarest Lepidoptera are reduced to existing only in the few remaining acres of intact habitat that have so far escaped the disruption that has come with settlement. We may only guess at what has already been lost.

Habitat Needs

The loss of open natural area via forest encroachment and deliberate tree planting is also detrimental to many Lepidoptera. Butterflies are particularly sensitive to this, since even our forest species prefer sunny openings, clearings, or edges rather than dense, unbroken woods. Maintaining and promoting native plant life is necessary for the continued well-being of our Lepidoptera, to provide for the needs of each stage of the life cycle, such as larval food plants and sources of nourishment and moisture for adults.

Rare Species

Wisconsin has 66 species of Lepidoptera listed as threatened, endangered, or special concern. Besides being rare in Wisconsin and dependent on the continued existence of scarce natural community types, they also are considerably restricted within North America. Twenty-nine of these species are associated with bogs and barrens and are described in the Online Field Guide to Rare Lepidoptera.

Although we know more about butterflies than any of the other insects, we still have an incomplete picture of the Lepidoptera fauna in Wisconsin, especially the moths. We must continue to inventory, monitor, and protect these rare Lepidoptera species so that we do not lose these valuable members of our natural heritage and consequently the other natural plants and animals intertwined with their survival.

Adapted from a 1990 article by Les Ferge.