Biological and systematic studies of the subgenus Neotrombicula (genus Trombicula) in the central United States (Acarina, Trombiculidae)

THE UNIVERSITY OF KANSAS SCIENCE BULLETIN Vol. XXXVI, Pt. I] June 1, 1954 [No. 4 Biological and Systematic Studies on the Subgenus Neo-trombicula ( Genus Trombicula ) in the Central United States (Acarina, Trombiculidae ) * By Ervin H. Kardos Ahstract: This paper consists of studies of larval chigger mites of the sub-genus Neotrombicula from the central United States. A key to all species known in this country is included, and two new species are described. Trombicula (Neotrombicula) autumnalis, hitherto known from Europe, is re-corded from America for the first time. Long series of specimens were examined whenever possible and considerable data on variations within populations and on geographical variations are pre-sented. This is particularly important since much of the previous work on chiggers has been done with very inadequate series of specimens even when long series were available. T. microti and T. harperi were found to behave as distinct species even though so similar that a few specimens could not be placed with certainty in one species or the other. T. lipovskyi and T. whartoni were also found to be distinct sympatric species although very closely related. Cer-tain characters which distinguish them in one area are of little value in another area where other characters are more useful. T. whartoni is restricted to moist, usually woodland areas while T. lipovskyi is found both in such areas and in dry treeless regions. Data on hosts and seasonal activity are provided for each species treated. Some of the other ecological requirements can often be inferred from the places where host animals were obtained and are presented whenever pertinent. Fur-ther biological data is provided for certain species, particularly T. lipovskyi and T. sylvilagi. Like other species of Neotrombicula occurring in the Kansas region, these forms are active as larvae in fall and winter. Larvae of the first are abundant in Kansas from October through December, become scarce in late December, January, and February, and show a lesser peak of activity again in March and April. Larvae of T. sylvilagi are active in the same area from the last half of August to the first half of December. Both species, and perhaps all "winter chiggers," have but one generation per year, in contrast to at least some of the forms whose larvae are active in summer ( e. g., T. alfreddugcsi ) . In T. lipovskyi engorged larvae dropping from hosts in November became nymphs under outdoor temperatures from April to July and the first adults appeared in late June. * Contribution number 838 from the Department of Entomology, University of Kansas. (69)