48 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I28 



scutal setae ; thin ; very sparsely plumed. With about 42 ventral setae 

 of which about 16 are postanals. True ventrals about 18 to 21 mi- 

 crons in length ; thin ; pinnae inapparent. Legs: Coxal setae all thin, 

 weakly plumed. Coxa III with 2 setae, one near anterolateral angle, 

 the second near base of coxa. Coxa III broad, in ratio of 66 (length) 

 to 59 microns ( = 1.12). First pair of sternal setae with bases almost 

 contiguous, about 28 microns in length. Second pair of sternals at 

 level of coxa III ; widely separated so that each is in line with base 

 of coxa II ; resembling coxal setae. Sensory setae as in G. exilis, 

 new species. 



Ty\pe material. — Holotype (No. B- 19389-5) and 55 paratypes (No. 

 B-19389) ex Rattus whiteheadi whiteheadi Thomas (completely em- 

 bedded in female perineum). North Borneo, Mount Kinabalu, Mari 

 Parei, elevation 5,100 feet, August 27, 1953 (R. Traub, for joint U. S. 

 Army-Colonial Office Medical Research Unit). Two paratypes, ibid., 

 but August 25, and recovered by washing the host by a modifica- 

 tion of the Lipovsky detergent method (Lipovsky, 1951). One para- 

 type, ibid., but at Tenompak, elevation 4,500 feet, August 29 (along 

 with 5 G. ampullata, new species), Holotype (U.S.N.M. No. 2170) 

 deposited in U. S. National Museum. Paratypes distributed as for 

 G. exilis, new species. 



Comment. — It is of interest that this species can burrow completely 

 into the superficial skin tissues of the host. The No. B-19389 series 

 was collected by dissection after noting that the surface of perineum 

 of the rat was pock-marked by a series of smooth pores. The pores 

 were thereupon enlarged by means of fine forceps or dissecting needles 

 and the chiggers were found just below the opening. Except in the 

 instance of unengorged (hence recently attached) chiggers, the chig- 

 gers were entirely within the pocket, and no part of the body pro- 

 truded through the aperture. If present, the chiggers were solitary 

 within these pockets. Many of the larger pores led to empty pockets, 

 indicating that the chiggers had emerged. This burrowing phenome- 

 non has not been noted for any other species of chigger by the Ameri- 

 can and British field teams in Assam, Burma, Malaya, or Borneo, 

 and this is apparently the first report of a chigger which may charac- 

 teristically burrow into mammalian tissues.^** It is obvious, however, 

 that a chigger that penetrates into the tissues of a host may readily 

 escape detection, and other such species may in reality be common in 

 nature. In this regard it should be pointed out that subsequent to the 



^'^ Apolonia tigipioensis Torres and Braga, 1939, penetrates the quills of South 

 American birds and has been once reported as having entered the skin on the 

 buttocks of a human in Brazil (Carneiro, 1949). 



