116 PROCEEDINGS OF THE NATIONAL MUSEUM VOL. 106 



of the legs may be decorated with punctations, or pimctae. 

 Punctae are usually described as pits in the cuticle. 



Within the basic chigger pattern the genus Euschongastia, as 

 it is now known in North America, has its own basic form (figs. 

 1-3). The size varies but all specimens have been less than a 

 millimeter in length. Measurements are made from specimens 

 preserved on slides. The length is the over-all measurement from 

 the posterior edge of the body to the most anterior extension of 

 the body or the gnathosoma. The width is the widest dimension. 

 Shape, unless otherwise indicated, is taken from specimens pre- 

 served on slides. Color is recorded from living specimens. 



The gnathosoma is compact and somewhat cone-shaped. The 

 palps have five segments. The basal segments of the two palps, 

 the coxae, are fused to form a single ventromedian plate. It is 

 usually marked with punctae. Also fused with it are the tro- 

 chanters, although the line of fusion often can be determined. 

 At the anterolateral corners of the fused coxae, posterior to the 

 union with the trochanters, is a pair of curved setae with setules 

 along the outer curvature. The palpal coxa is often referred to 

 as palp 1 in descriptions and drawings. The palpal femur, palp 2, 

 swells forward and upward. It is rounded laterally on the dorsal 

 aspect but usually is somewhat excavated on the posterolateral 

 surface from the ventral aspect. It bears on its dorsal surface, 

 posterolaterally, a single seta which curves anteriorly. The seta 

 is covered with setules except that the concave curvature adjacent 

 to the palp tends to be nude. The palpal genu, palp 3, is a short 

 truncate cone smoothly continuing the taper of the femur. On 

 its dorsal surface is a single forward-curving seta which usually 

 bears setules on the convex curvature. In two species normally 

 and in a third occasionally, the seta is nude. The palpal tibia, 

 palp 4, continues the taper of the genu and terminates in the 

 palpal claw. It bears three setae. The first tibial seta is a 

 forward-curving dorsal which usually has setules on the outer 

 curvature. The second is lateral. It varies in different species 

 and is much used as a taxonomic character. It may have numer- 

 ous setules on its outer curvature and be described as pectinate; 

 it may bear only one or more setules, which can be counted easily, 

 and be described as forked or branched; or it may be entirely 

 nude. The third tibial seta is ventrolaterally placed. It usually 

 projects laterally, and in all species except one has setules over 

 the longitudinal dorsal half of the shaft. The palpal claw is 

 divided into two to seven prongs in different species. When the 



