An atypical larval color form of Baetis intercalaris (Ephemeroptera: Baetidae) from Pennsylvania and the Kiamichi River basin of southeastern Oklahoma

An atypical larval color form of Baetis intercalaris was discovered and reared from the Kiamichi River basin of southeastern Oklahoma. Identical nymphs were also recently discovered in northeastern Pennsylvania This atypical larval color form has been previously reported only from Wisconsin. Larvae of this color form are visually distinctive because they lack the pale triad of spots along the posterior margins of most abdominal tergites diagnostic of the typical color form. The atypical form is uniformly marked on each tergite with pale, anterior, paired incurved lines (parentheses like) on a gray or brown background, lacking the paler abdominal tergites and spots characteristic of typical B. intercalaris. No morphological characters in the adult stage or the larval stage were found to support establishment of a new species.