14 PROCEEDINGS OF THE NATIONAL MUSEUM Vol.68 



as broad ; segment III distinctly longer than broad and longer than 

 IV; segment IV about as broad as long; segment V only slightly 

 longer than broad and equal to III in length. Macrochaetae of 

 thorax medium, subequal ; macrochaeta I about two-thirds as long as 

 the width of coxa I ; macrochaeta III situated slightly more than the 

 diameter of the bulb of thoracic spiracle behind the same. Posterior 

 marginal setae of thorax about 6 or 7 on each side, a larger pair near 

 the median plane and three large pairs situated laterally. Thoracic 

 spiracles the smallest of any species of the genus observed by the 

 writer, being 0.062 mm. in diameter across the bulb. Abdomen 

 large and long, segment VI slightly longer and slightly narrower 

 than V. Body setae small and hard to see, all the larger ones 

 arranged in transverse rows. Number of setae in transverse row on 

 ventral side of segment VI typically 10. Pleural plates (fig. 4, B) 

 very long and very broad; pleural plate I broader than long and 

 slightly lobed laterally; plate II very broad, distinctly lobed laterally 

 and with spiracle almost touching the anterior margin; plate III 

 much longer than II and much more strongly lobed ; plate IV larger 

 than III but of the same shape ; plate V the largest of all the pleural 

 plates and distinctly lobed laterally; plate VI small, broader than 

 long, and slightly lobed laterally; plate VII somewhat triangular, 

 slightly longer than broad. I..egs medium; femur I longer than 

 broad ; tibia I about twice as long as broad. Tubercle of femur III 

 large, with a deep notch in margin of leg next to it, bearing on 

 anterior side some distance from tip a seta shorter than tubercle 

 itself. 



Length of an average-sized, unengorged female, 2.95 mm. ; greatest 

 width, 1.35 mm, 



Male. — Leg I about the same length as the others but with the 

 tibia shorter and stouter and the tarsus slightly enlarged. Distal, or 

 chief, spine of thumb of tibia I extending beyond the margin of 

 thumb by a little over one-half its length; outer anterior accessory 

 spine very sharp, about one-half as broad as the distal spine and as 

 long as the same ; inner anteror accessory spine subequal with outer 

 anterior accessory spine and situated almost in the crotch of the tibia ; 

 ventral or posterior accessory spine long, setiform, about twice as long 

 as the distal spine. Pleural plates smaller but similar to those of 

 female, the first one somewhat differently shaped from the first plate 

 of the female, being broader in proportion to its length and more 

 irregular. 



Length of average-sized specimen, 2.45 mm.; width, 0.95 mm. 



T7j'pe host and type locality. — Ateles ater, from? 



Type slide.— Cat. No. 28106, U.S.N.M. 



Described from many males and females taken by Dr. E. A. 

 Chapin from an individual of Ateles ater which died in the National 



