22 IXODOIDEA^ OR TICKS, OF THE UNITED STATES. 



Stigmal plate (PL II, fig. 8; PI. IX, fig. 6) large, nearly circular, 

 with a circular peritreme, surface minutely granulate. 



Length of female shield, 1.7 mm. 



Male. — Body subrectangular, narrowed in front of third pair of 

 legs, broadly rounded behind. Shield not reaching to tip, with many 

 subequal punctures, some hairs near hind margin of body; venter 

 finely punctate; stigmal plate as in the female. Capitidum three 

 times as broad as long, with a median depression; mandibles about 

 one-half as long as palpi, hypostome still shorter, palpi (PL II, fig. 7) 

 cylindrical, third joint prolonged in an acute point, the fourth joint 

 projecting below from near the base. Legs rather slender; coxae 

 unarmed; the tarsi tapering, fourth with apical tooth and subter- 

 minal tubercle beneath. 



Length of male, 3.8 mm. 



Specimens come from St. Paul Island, Alaska, and Bering Island. 

 Birula records it from Unalaska, and Kramer and Neuman from 

 Bering Island. Cambridge described it from Kerguelen Island, Ant- 

 arctic Ocean, and Evans and others have taken it from the western 

 isles of Scotland. It is probable that the Ixodes urice of AVhite (a 

 manuscript name) from Arctic America is the same species. It 

 occurs on several large migratory sea birds. 



Genus IXODES Latreille. 



Venter showing a pair of submedian grooves reaching forward 

 from hind margin of body and connected in front of anus ; no groove 

 behind anus. Capitulum j^roduced anteriorly in the middle; porose 

 areas subtriangular. Palpi rather slender, at least in female, the 

 second joint usually twice as long as broad, the third not very much 

 shorter, longer than broad and tapering toward tip. Shield without 

 markings; no ocelli. Coxa I close to rostrum, with one or two teeth 

 behind ; coxa IV of male not enlarged. Posterior margin of body 

 without festoons. Stigmal plate circular or elliptic. Tarsi II, III, 

 and IV divided, the basal part shorter than the apical part, and no 

 tooth-like claw at apex. 



Type. — Ixodes ricinus Linnaeus. 



Our species are numerous, and probably there are several yet to 

 be found by more thorough exploration. 



Table of the Species. 



1. Tarsus I fully one and one-half times as long as the metatarsus 2 



Tarsus I barely more than one and one-fourth times as long as the 



metatarsus 



2. A stout backward-directed tooth on under side of rostrum from near 



base of each palpus; shield fully twice as long as broad, with def- 

 inite lateral carinas ; porose areas about as long as broad diversifossus. 



No such teeth on rostrum below, at most only a tubercle ; shield 

 broader, and rarely with definite cariniie; porose areas plainly 

 broader than long 3 



