CHIGGERS — FARRELL 131 



Eyes: Two pairs in ocular plates lateral to the posterolateral 

 setae; corneas distinct. Diameter of anterior eyes, 10; of post- 

 erior eyes, 9. 



Dorsal setae: Similar in form to scutal setae; setules small. 

 Length of a humeral, 50; of a seta from the first posthumeral 

 row, 38 ; of a posterior seta, 36. 



Dorsal formula of the single paratype : 2.6.6.4.4.2. 



Ventral setae : Clearly of two forms ; sternals and poststernals 

 occupying the region just anterior to the anus similar to non- 

 specialized leg setae, with rather long, straight setules on side 

 opposite bodj''; just anterior to the anus the form changes ab- 

 ruptly to that of the dorsal setae. Length of a first sternal, 44; 

 of a second sternal, 42; of a seta from the first posternal row, 

 37 ; of a posterior seta, 36. 



Ventral formula of the single paratype : 2 . 2 plus about 19. 



Material : A single paratype borrowed from the U. S. National 

 Museum. From host : 



Man 



Mexico, D. F., Mexico, July 1944. 



Diagnosis: E. nunezi is the only species of the genus now 

 known in North America w^hich has all nude setae on th« palpal 

 tibia, a pointed seta on the palpal tarsus in addition to the spur, 

 and a mastitarsala IIL 



Remarks : This species is known only from the original collec- 

 tions in Mexico. It was found on man, parasitizing all members 

 of one fam.ily, and on chickens in the same location. E. nunezi 

 is the only species of the genus in North America reported as a 

 parasite on man. 



4. Euschongastia trigenuala, new species 



Figure 4,a; Plates 4, 6, 10 



Description : Size : Length, 480 to 510 ; width, 345 to 370. 



Shape : Oval to ovoid. 



Gnathosoma: Seta on palpal femur rather small with few 

 setules. Genu with a curving, nude seta. Dorsal seta on tibia 

 with a row of setules along its outer curvature ; lateral seta nude ; 

 ventral seta rather small with few setules. Palpal claw curved, 

 usually with five prongs, median prong longest, two accessories 

 slightly shorter, and two smaller on the outer curvature. Cheli- 

 ceral base heavy; blade with distinct subapical dorsal and ven- 

 tral teeth. Galeal seta nude. Palpal coxae and cheliceral base 

 punctate. 



