Art. 19 LICE OF THE GENUS PEDICULUS EWING 17 



medium in length, II slightly longer than I and III ; macrochaeta 

 I about two-fifths as long as width of coxa I; macrochaeta III 

 about the diameter of thoracic spiracle behind the same. Posterior 

 marginal setae of thorax typically six on each side, all spinelike 

 but the outer one and the third from the outer end of row very 

 minute. Thoracic spiracles medium, spiracular bulb 0.110 mm. in 

 diameter. Abdomen very large and in case of some females much 

 distended by developing egg; most of abdominal setae in trans- 

 verse rows, the dorsal ones two or three times as long as the ventral 

 ones; setae in transverse row on ventral side of sixtli abdominal 

 segment typically 8 but varying from 7 to 9. Pleural plates 

 usually rather poorly chitinized and poorly pigmented; plate I 

 broader than long and not squarish; plate II broader than long 

 and squarish, spiracle situated slightly in front of the middle; 

 plate III about equal in length and breadth, spiracle slightly in 

 front of middle; plate IV the largest of all the pleural plates, 

 longer than broad and slightly broader than III; plate V as long 

 as IV but not so broad ; plate VI small, spiracle behind the middle ; 

 plate VII almost circular, but varying much in shape. Legs 

 slender; femur I about one and a half times as long as broad; 

 tibia I about two and a half times as long as broad. Tubercle of 

 femur III varying in size, low, usually only a slight notch in leg 

 inside of tubercle, seta on tubercle about twice as long as tubercle 

 itself. 



Length of an average-sized, unengorged female, 3.80 mm. ; greatest 

 width, 1.40 mm. 



Male. — Leg I stouter than in female with thumb much larger; 

 tibia I about twice as long as broad; distal, or chief, spine of 

 thumb of tibia I not extending beyond the margin of the thumb by 

 half its length ; outer, anterior accessory spine setiform, almost 

 three times as long as the terminal spine itself; inner anterior 

 accessory spine rather slender and slightly longer than the terminal 

 spine; posterior accessory spine almost setiform, being much 

 smaller but about as long as the inner anterior accessory spine. 

 Chaetotaxy of distal end of left hind tibia (fig. 5) as follows: 

 Distal, or chief, spine extending beyond the tip of margin of process 

 by about three-fourths its length; outer, anterior accessory spine 

 about two and a half times as long as distal spine; inner, anterior 

 accessory spine about as long as distal spine and situated in crotch of 

 tibia ; posterior accessory spine longer than distal spine and about as 

 stout as the inner, anterior accessory spine. Pleural plates not 

 essentially diff'erent from those of the female, plate I appears to be 

 a little more irregular in shape and somewhat smaller than in the 

 female. 



