Evidence of long range transport of a dark morph swallowtail butterfly (Papilio glaucus) on a storm front into northern Michigan (Lepidoptera: Papilionidae)

A dark morph female Papilio glaucus was captured in the middle of a P. canadensis population in the center of Dickinson County, in Michigan's Upper Peninsula. We are unaware of any dark female ever being captured at this latitude, and none within 400 km has ever before been reported. Morphological wing traits all score this dark female as P.! glaucus, with all 31 of the other (yellow) females captured from the same group of nectar sources scoring as Il canadensis. Two diagnostic electrophoretic allozymes (PGD and LDH) show all 24 males to have 100% P. canadensis alleles, and 98% canadensis alleles were seen for the HK locus. The dark female had the P. glaucus X-linked allele for PGD, the P. canadensis X-linked allele for LDH, and was heterozygous for diagnostic HK alleles which are autosomal. All other yellow females that were examined were pure canadensis type for the sex-linked PGD and LDH alleles. One yellow female was heterozygous for the autosomal HK diagnostic alleles. Along distance "blow-in" on a strong weather front from the southwest is suspected as the most likely explanation for the appearance of this dark morph female of mixed (introgressed) genetic background so far from its nearest known source. The blow-in was not likely to have been in a previous year since this dark morph female would require both (1) a dark morph mother with the Y-linked dark gene and (2) a father that was part I! glaucus (i.e, without the color suppressor genes and with a PGD-100 allele). None of the males from this area had PGD or LDH alleles of the canadensis type this year or ever previously, making it unlikely that the blow-in occurred in a previous year.