44 MISC. PUBLICATION 5 00, U. S. DEPT. OF AGRICULTURE 



posterior tarsus with 5 pairs of lateral plantar bristles, the first pair not being 

 shifted ventrally. Abdomen with but few apical spines. Tergal plate VII with 

 a small, posterior, median process. Female with 1 or 2 antepygidial bristles 

 on each side of abdomen and a single receptaculum seminis. In male, sternal 

 plate VIII with large, fringed, membranous flap; sternal plate IX with large, 

 inner, vertical processes, an anterior median apophysis, and long, 2-lobed, posterior 

 processes ; movable finger of clasper large, broad, flat, somewhat rectangular and 

 with 3 pigmented, marginal spines. 



This genus, not being given in Dalla Torre's catalogue, was over- 

 looked at the time Boreopsyllus was established. 



MlOCTENOPSYLLA ARCTICA Rothschild 

 (Fig. 5, B) 



Mioctenopsijlla arctica Rothchild, 1922, Rpt. Norwegian Exped. Novaya Zemlya 



1921, No. 4, p. 4, figs. 1-5. 

 Amphipsylla harficeni'Exvmg, 1927, Wash. Biol. Soc. Proc. 40: 89. 



Type host. — Rissa tridactyla (L.) (Atlantic kittiwake). 



Type locality. — Gribovii Fjord. Novaya Zemlya. 



Range. — Novaya Zemlya, Alaska, and probably most of coastal 

 regions inside of Arctic Circle. 



Notwithstanding the fact that Amphipsylla hadweni Ewing was 

 described from North America, while Miocten&psylla arctica Roths- 

 child came from Novaya Zemlya, the two forms appear to be identi- 

 cal. The species should be regarded as circumpolar. It is well illus- 

 trated by the figures which accompany Rothschild : s original descrip- 

 tion. 



The Genus Thrassis Jordan 



(Fig. 7, A) 



Thrussis Jordan, 1933. Novitates Zool. 39: 72. Type, Ceratophyllus acamantis 

 Rothschild (by original designation). 



Frontal tubercle small, apically angulate. Forehead with but a single row 

 of lateral setae, the ocular row. Eyes well developed, fully pigmented. Labial 

 palpus 5-segmented, extending to or beyond apex of trochanter I. Postan- 

 tennal region of head with a single row of sota^. the marginal row. Pronotal 

 comb with usual, long, black spines. Femur I with several lateral setae ; 

 coxa III without a row or patch of spinelets on the inner surface ; segment 

 I of posterior torsus not longer than II, III, and IV taken together; last seg- 

 ment of each tarsus with' 5 pairs of lateral, plantar bristles, the first pair being 

 in line with the others. Abdomen with but few apical spines, all of which 

 are situated dorsally. Tergal plate VII with either no posterior, median process, 

 or a very small one. Two or 3 antepygidial bristles on each side of abdomen 

 in female; 1 long and 2 minute setae on each side in male. Female with 1 

 receptaculum seminis, the head of which is spherical or subspherical : stylet 

 with 2 or 3 prominent lateral bristles. In male, sternal plate VIII large, 

 broad, without long, filamentous, apical appendage; sternal plate IX with 

 long, slender, elbowed, inner vertical processes, a somewhat enlarged anterior 

 apophysis, and a posterior process which usually has 2 lobes and a pair of 

 pigmented spines; movable finger of clasper broad, flat, curved, with a few 

 long setae on posterior margin. 



The posterior process of the ninth sternal plate of the male in 

 this genus has never been properly studied. Male specimens should 

 have the modified abdominal segments dissected so as to show the 

 structure of this process and also that of the penis, which is of almost 

 equal taxonomic importance. Thrassis is exclusively a Nearctic 

 genus. Its species parasitize various rodents. 



