86 PROCEEDINGS OF THE NATIONAL MUSEUM ^^^- ^^^ 



1952. To all other persons who contributed materials or infor- 

 mation, the author is also very grateful. 



Chiggers are the larvae of trombiculid mites. They are the 

 first active developmental stage in a life history which includes 

 seven steps — egg, deutovum, larva, nymphochrysalis, nymph, 

 imagochrysalis, and adult. Although very small, they can be seen 

 by the naked eye. They are important parasites of terrestrial 

 vertebrate animals, and they are the only stage of the trombiculid 

 life cycle which is known to be parasitic. So far as is known, the 

 two other active stages, nymph and adult, are predacious on small 

 arthropods and arthropod eggs. Chiggers are widely distributed 

 throughout the world. Several species are irritating pests of 

 man. Wherever these species occur they have been given common 

 names by the people living there ; and they are known by reputa- 

 tion in places beyond where they are found. 



Recently there has been a great awakening of interest in the 

 study of chiggers. During World War II, under the medical 

 urgency to find out everything possible concerning the vector of 

 scrub typhus in the Pacific area, intensive investigations were 

 begun. The interest aroused in this effort, which still continues, 

 has spread to chiggers in general and has brought about rapid 

 development in the systematics of the group. 



Few areas have been studied intensively. Experience indicates 

 that whenever a new region is investigated new forms as well as 

 known species will be found. From September 1947 until Decem- 

 ber 1949 small mammals were trapped in Duke Forest, Durham 

 County, and Orange County, N. C, for the purpose of determining 

 the chigger populations. During the same time, chiggers removed 

 from mammals collected by the Pennsylvania Mammal Survey 

 were sent to Duke University for identification. A number of 

 shipments were received from Ohio. The most numerous chigger 

 specimens and species secured were of the genus Euschongastia. 

 With these collections as a nucleus, a study of the systematics of 

 the genus for North America was undertaken. 



Review of the literature 



Systematics : There has been some confusion in the historical 

 development of the family Trombiculidae. For many years the 

 life histories of the mites were unknown; and, when different 

 developmental stages were collected, they were named independ- 

 ently. Later, as life histories were determined, shifts of nomen- 

 clature were required by application of the law of priority. 



