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How To Identify Common Species of Migratory Butterflies

Many species of migratory butterflies have distinctive patterns and are easy to identify. Others are not particularly distinctive and can be confused with similar migratory or non-migratory species. Easily identified species include buckeyes, mourning cloaks, and red admirals. monarch on aster Problem migratory species, with many look-a-likes, include cloudless sulphurs, pipevine swallowtails, most of the angle wings, and fritillaries. Ironically, the single best know and most studied species, the monarch butterfly is also a problem species with two look-a-likes, the queen butterfly (migratory), and the viceroy butterfly (non-migratory). Because viceroy butterflies do not migrate and are not particularly abundant when monarch butterflies are making their spring and fall migrations, viceroys are unlikely to be picked up by our sampling techniques. Fortunately, monarch butterflies are usually much more abundant than queen butterflies during the migration period, minimizing the risk of errors due to mistaken identification. In any case, it is essential for researchers in this project to get a good field guide, a pair of binoculars, and a butterfly net (which can double as a wind sock), and practice identification in the field. Some species with highly distinctive markings can be identified by viewing them through binoculars. However, most species will have to netted and examined at close range. As noted above, monarchs fall into the second category. Over the years I have netted 'monarchs' flying among vegetation that turned out upon closer examination to be viceroys, queens, and on one occasion, a large gulf fritillary.

The need for practice in species identification brings up another topic. How can a field researcher convince others that their identifications are accurate? After all, everyone makes mistakes (see above). I've even received photographs of a tiger swallowtail from someone who believed that they had photographed a monarch butterfly. Voucher specimens and/or good quality photographs are the only way around this problem. In my opinion, voucher specimens are the better of the two options. Photographs can ensure that an identification was correct but present practical problems. Monarch butterflies are abundant, large, showy, tend to roost in clusters, and while nectaring, almost seem to pose for the camera. Most other migratory butterfly species are less cooporative. They are usually less abundant than monarchs, less brightly colored, smaller, solitary, and camera-shy, tending to fly off as soon as you approach. Finally, because the top and bottom surfaces of the wings can be equally important for identification, at least two high quality photographs are required for many species. On the other hand, preserved voucher specimens can be examined at leisure and may even serves as resource material for future DNA analysis. The last point is important. Migratory and non-migratory populations of some species may eventually prove to have significant genetic differences. If there is a change in the distributions of the two types over the years, voucher specimes could indicate how things once were 'back then'. In in case, if you decide to collect voucher specimens, several individuals of each species should be plenty.