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The Natural Communities of Iowa and Their Butterflies
- University of Iowa Press
- Chapter
- Additional Information
utterfly species are not randomly distributed in Iowa. They live only where their requirements for life are met. These include places where egg‑laying, lar‑ val feeding, pupation, mate selection, and adult nectaring can occur. While some common species, including the Cabbage White, Sachem, Clouded Sul‑ phur, Silver‑spotted Skipper, Common Sootywing, Pearl Crescent, and Eastern Tiger Swallowtail, can undertake these activities in a wide variety of habitats, others are much more selective. For those species, only a very limited number of places will provide habi‑ tat through all the stages of their life cycle. For example, Sleepy Duskywing adults are most commonly seen in xeric glade prai‑ ries of northeastern Iowa, where they search for mates and find nectar sources. The larvae, however, feed on oaks in the surrounding woodlands. Without both of these habitats, populations of the Sleepy Duskywing could not survive. In species with limited habitat requirements such as this, populations are restricted to areas in which the proper association of vegetation types is present. Potential sites for these uncommon species can be located by identifying such areas of suitable habitat. Geologists have divided Iowa into eight landscape regions (Prior 1976): the Paleozoic Plateau, Iowan Surface, Southern Iowa Drift Plain, Des Moines Lobe, Northwest Iowa Plains, Loess Hills, Missouri Alluvial Plain, and Mississippi Alluvial Plain. Within each of these distinctive landscapes a number of unique habitats occur. Just as each habitat supports a characteristic flora (see Eilers 1982, for instance), each has also been found to harbor distinctive butterfly faunas. In this chapter, the butterfly faunas of the important natural habitats within Iowa’s landscape regions are briefly discussed. Only species considered to be naturally repro‑ ducing in Iowa are included; migrant species generally show few habitat preferences. Generally, the Iowan Surface, Paleozoic Plateau, and northwestern section of the Des Moines Lobe have been fairly well biologically documented. Other landform regions of the state have a much less well known lepidopteran fauna, however. More intensive sampling will undoubtedly uncover many additional species and associations from the habitats found in these regions. The Natural Communities of Iowa and Their Butterflies B | a n i n t r o d u c t i o n t o i o wa b u t t e r f l i e s Paleozoic Plateau The northeastern corner of Iowa is well known for its rugged topography. This region was once termed the driftless area by early Iowa geologists, who believed no glaciers had covered the area. With the discovery of pre‑Illinoian drift deposits on this landscape, however, it is now clear that the Paleozoic Plateau was glaciated at the same time as the surrounding terrain (Prior et al. 1982). The rugged nature of this region was apparently caused both by permafrost action and by Mississippi River down‑cutting within the last twenty thousand years (Hallberg et al. 198). The removal of glacial till by these erosive factors has allowed development of the only completely bedrock‑controlled land‑ form region in Iowa (Prior 1976). A number of interesting habitats are found within this landscape. Woodlands Woodlands are the most common native habitat remaining within the Paleozoic Pla‑ teau. They are primarily found on the steep, rocky land adjacent to streams and rivers. Limestone cliffs are frequently present. Many of the remaining woodland areas have been severely disturbed by grazing. A relatively large amount of woodland habitat remains throughout the state, not just in the Paleozoic Plateau, so most of the butterflies associated with it are widespread. These include the Juvenal’s Duskywing, Hobomok Skipper, Silver‑spotted Skipper, Dun Skipper, Banded Hairstreak, Eastern Comma, Question Mark, Mourning Cloak, Red Admiral, Red‑spotted Purple, Hackberry Emperor, Tawny Emperor, and Little Wood‑satyr. Some of the uncommon or rare species of woodlands include the Sleepy Duskywing, Harvester, Hickory Hairstreak, and Columbine Duskywing. The Columbine Dusky‑ wing may be limited to Paleozoic Plateau woodlands. These rarer species seem to be re‑ stricted to only the largest and most undisturbed woodlands. One of the rarest resident butterflies in the state, the Compton Tortoiseshell, may be observed in a few areas of Allamakee and Dubuque counties where large groves of paper birch are present. Adults seem particularly fond of trails or roadsides near streams. Most of Iowa’s woodland butterflies exhibit an affinity for openings and edges, prob‑ ably because mate location is easier due to the higher light levels and visibility. At times literally hundreds of individuals may be seen along deserted stretches of...