CHIGGERS — F ARRELL 219 



the species. Also, relative lengths of empodium and claws are 

 often characteristic. These characters are included in the de- 

 scriptions. At the present time it is not necessary to use them in 

 diagnoses. 



The method used in this paper to illustrate the descriptions of 

 species of chiggers logically follows the method of study. Wharton 

 (1947a) reported a shorthand system of taking notes on chiggers 

 by making a series of drawings of morphological details. His 

 method was used during the present study and was adapted for 

 the illustrations in this paper. It represents a departure from the 

 usual methods of authors. For example, Gunther (1940) drew 

 the scutum, the cheliceral blade, and longitudinal halves of the 

 dorsum and venter. Womersley (1944) also drew the scutum, but 

 he included a ventral view of the gnathosoma, a dorsal view of 

 the tarsus of the first leg, and full views of the dorsum and 

 venter. Brennan (1948) included drawings of the scutum and 

 longitudinal halves of the dorsum and the venter; in addition 

 he illustrated a longitudinal, dorsal half of the gnathosoma. In 

 the present paper the drawing of the scutum has been included ; 

 but almost all the other drawings of earlier authors have been 

 omitted. There is little variation in the general organization of 

 the body in species of Euschongastia. The arrangement of the 

 parts of the body is shown in figures 1 and 2. Such drawings have 

 not been repeated for the species. Drawings of the dorsum and 

 venter frequently do little more than show the number of setae 

 and have been omitted. However, reflecting the emphasis in this 

 paper placed on structures of the gnathosoma and the legs, a 

 whole series of drawings illustrating details of these parts has 

 been included. The drawings present the chigger in a highly 

 dissected manner, but they are the direct result of giving atten- 

 tion to the whole mite rather than to a few restricted features. 

 When the gnathosoma and the legs were included in the study, 

 the higher magnifications of oil immersion lenses became neces- 

 sary to study these features in detail. With such a method of 

 study, the field of view is reduced and attention is given succes- 

 sively to separate small units. The present system of illustrating 

 the descriptions was adopted as a practical method of presenting 

 the characters on a scale sufficiently large to be useful. 



Recently, photomicrography has been used as an aid to the 

 study of the systematics of chiggers. Gill and Parrish (1945) 

 gave directions for photographing the scuta of chiggers by using 

 oblique light from the condenser to outline the structures more 

 sharply. The method was employed by Brennan (1948) to obtain 



