Loomis and Wrenn (1984, Pg. 152- 159 In Acarology IV, Vol. 1, Ellis Horwood Ltd., Chichester, UK) proposed a redefinition of the pest chigger genus Eutrombicula Ewing, 1938, stating that a number of records were misidentified and many new species remained to be named. Neither author survived to undertake a revision of Eutrombicula, but Wrenn had begun a study of the abundant pest chiggers of the eastern United States. Significantly, this genus includes a species, currently treated as E. alfreddugesi (Oudemans), that is the most frequent human-biting pest chigger in much of the eastern United States, although it has low host specificity and has also been recorded as an ectoparasite of a variety of amphibians, reptiles, birds, and other mammals (Wharton and Fuller 1952, Mem. Entomol. Soc. Wash. No. 4; Loomis 1956, Univ. Kansas Sci. Bull. 37:1195 - 1443; Loomis and Wrenn 1984).
Originally, a single widely distributed species was thought to extend from the eastern United States into the Great Plains and south into Mexico. Thus, Fuller (1952, Zool. Verhand. No. 18), in studies of the A. C. Oudemans collection, argued that Microthrombidium alfreddugèsi Oudemans, 1910, was the available name for that species, despite the fact that the type locality was in southern Mexico. This no longer seems likely. The description of M. alfreddugèsi was based on 4 specimens from near Tejupilco, Mexico. Given that some 80 species of Eutrombicula are now known from the Western Hemisphere, many of them tropical, it is doubtful that the 2 poorly mounted specimens in the Oudemans collection (Fuller 1952) are members of the common Eutrombicula species found in eastern North America.
Extensive synonymies for E. alfreddugesi were given by Fuller (1952) and Wharton and Fuller (1952). The next available name for the species appears to be Trombicula cinnabaris Ewing, 1920, based on an adult trombiculid from East Falls Church, VA. Ewing (1920, Ann. Entomol. Soc. Am. 13: 381 - 390) also reported other specimens from North Beach, MD. Later, Ewing (1925, Proc. Biol. Soc. Wash. 38:17 - 20) obtained adults of T. cinnabaris from Stone Valley, PA and placed them in “breeding cells.” Larvae obtained from those adults were determined by Ewing as Trombicula irritans (Riley) (= E. alfreddugesi of authors). Ewing (1938, Proc. Biol. Soc. Wash. 50:167 - 174) erected the genus Eutrombicula and designated Microthrombidium alfreddugesi Oudemans as the type species for the genus. This generic reassignment has been followed by most recent authors, although Wharton and Fuller (1952) and Wolfenbarger (1952, Ann. Entomol. Soc. Am. 45: 645 - 677) treated Eutrombicula as a subgenus of Trombicula Berlese, 1905.
Among Wrenn's chigger collections shipped from California (by S. G. Bennett) to the Georgia Museum of Natural History, were specimens of T. cinnabaris and the reared larvae mentioned by Ewing (1925). The slides were on loan to Wrenn from the U. S. National Museum and have now been returned to that institution. D. A. Crossley reexamined the specimens and found that the holotype consists of the propodosoma of an adult Eutrombicula. The scutum (dorsal plate) and body setae are consistent with the illustrations of E. alfreddugesi nymphs shown in Crossley (1960, Univ. Kansas Sci. Bull. 40: 135 - 321). Furthermore, the larval specimens agree with the description of E. alfreddugesi given by Wolfenbarger (1952) and possess palpal claws with a moderate cleft typical of E. alfreddugesi (see the illustration in Loomis and Wrenn 1984).
Evidently, Wrenn had concluded that E. cinnabaris was the best available name for the species previously called E. alfreddugesi. He used the name cinnabaris in a developmental study in 1998 (Tuegel and Wrenn 1998, Int. J. Acarol. 24:199 - 211) and in a faunistics survey in 2004 (Reeves et al. 2004, Zootaxa 647: 1 - 20). He also recommended its use in studies published in 2000 and 2003 (Durden et al. 2000, J. Vector Ecol. 25: 222 - 228; Wilson and Durden 2003, J. Biogeography 30:1207 - 1220).
We concur with the replacement of the name E. alfreddugesi with E. cinnabaris, but with the caveat that common North American pest chiggers will likely prove to be a complex of species. As Loomis and Wrenn (1984) noted, the genus Eutrombicula in temperate North America needs to be revised.
Author notes
2Georgia Museum of Natural History, University of Georgia, Athens, Georgia 30602 USA.
3Department of Biology, Georgia Southern University, Statesboro, Georgia 30460 USA.
5Department of Plant and Environmental Protection Sciences, 3050 Maile Way, University of Hawaii, Manoa, Honolulu, Hawaii 96822 USA.