REVISION OF MOTHS OF PRODOXINAE 45 



County and Los Angeles County, southward along the coastal ranges 

 to northern Baja California. 



Discussion.— Throughout most of its nomenclatoral history, the 

 subspecies which Henry Edwards originally described as Thia extranea 

 was not recognized as a member of the Prodoxinae. Instead, this 

 insect was known as a yucca moth under the name of its junior 

 synonym, Tegeticula aterrima. Edwards originally placed Thia 

 extranea in the Heterogynidae and stated that it was closely related 

 to Atychia Latreille. Dyar (1903a) examined Edwards' series of two 

 syntjrpes and concluded that Thelethia {=Thia) extranea should be 

 included in the Yponomeutidae. Undoubtedly influenced by 

 Edwards' statement concerning the generic affinities of T. extranea, 

 Meyrick (1913) transferred it to the Glyphipterygidae along with 

 Atychia. In his checklist, McDunnough (1939) followed Meyrick's 

 decision and placed the monotypic genus Thelethia in the Glyph- 

 ipterygidae. In addition, he included Tegeticula aterrima in the 

 Prodoxidae as others had done before him. Perhaps relying solely 

 upon Edwards' description, Busck (1947) correctly associated 

 Thelethia extranea as the senior synonym of Tegeticula aterrima. 

 With the assistance of Mr. Alex Wyatt of the Chicago Natural 

 History Museum, the author was able to locate one of Edwards' 

 syn types. Through the cooperation of Dr. H. B. Cunningham of the 

 lUmois Natm'al History Survey, I was able to examine this specimen 

 and, thus, to confirm Busck's synonymy. 



The taxonomic status which I have recognized for Tegeticula 

 maculata extranea later may not be found to reflect its true relation- 

 ship ; instead, it may be decided that this moth deserves the status of 

 a distinct species. The fact, however, that T. m. extranea represents 

 a melanic derivative of T. m. maculata seems certain. Morphologi- 

 cally T. m. extranea is identical to its ancestral form in aU respects 

 except color and size. These differences, along mth distributional 

 peculiarities, suggest a degree of speciation greater than that usually 

 encountered in melanic forms. Primarily for these reasons, I have 

 treated this moth as a subspecies. 



Melanism in Lepidoptera has been grouped into three general 

 categories by Kettlewell (1961a) : (a) industrial, (b) relict or geogi-aph- 

 ical, and (c) semilethal. The type which T. m. extranea demon- 

 strates is apparently that of reUct or geographical melanism. Species 

 demonstrating this type of melanism typically occupy rather spe- 

 ciaHzed habitats characteristic of northern clunates, such as mountain 

 tops or high latitudes. For example, among those melanic Lepidop- 

 tera occurrmg in the Shetland Isles studied by Kettlewell (1961b), the 

 dark forms invariably were distributed farther north than the lighter 

 forms. In the sam.e reference, Kettlewell (p. 394) further concluded 



