20 IXODOIDEA^ OR TICKS, OF THE UNITED STATES. 



Family IXODID^. 



Dorsum of the body more or less covered by a corneous shield ; 

 head distinct in front of body; anus behind middle of venter; skin 

 finely striated. Coxse more or less separated ; tarsi with a pulvillum. 

 Stigmal plate behind coxa? IV. Male with dorsum almost entirely 

 covered by the corneous shield ; in the female the shield is restricted 

 to the anterior part of dorsum, and there are on the capitulum a j^air 

 of porose areas, not seen in males or in immature stages. 



The genera and higher groups known from our country may be 

 separated by the following table : 



Table of the Genera. 



1. ^'enter showing a curved groove a short distance in front of the anus and 



extending baclv each side to the hind margin ; no posterior marginal 

 festoons; stigmal plate nearly circular; no ocelli; hind coxa* of male 



not enlarged (Ixodinie.) 2 



Venter showing more or less distinctly a curved groove behind the anus, 

 but none in front of it; the male with distinct marginal festoons, more 

 or less distinct in the female (Amblyommina?.) 3 



2. Capitulum slightly angulate on the sides; palpi with the third joint 



shorter than broad, and broadly rounded Ccratixodes. 



Capitulum not angulate on sides; palpi with the third joint longer than 

 broad, and slightly tapering toward the tip Ixodes. 



3. Sides of capitulum angulate; ocelli present; male with anal i)lates; paljil 



very short - (lihipicephaliui.) 4 



Sides of capitulum not angulate 5 



4. Palpi with acute transverse ridges; stigmal plate nearly circular; i)orose 



areas elliptical, distant; no distinct groove behind anus Margaroims. 



Palpi without transverse ridges; stigmal plate comma shaped; porose 

 areas triangular, approximate; a distinct groove behind anus, 



Rhipicephalus. 



5. Outer angle of the second joint of the short palpi acutely produced; no 



ocelli; male without anal plates (Htemaphysalini) H(emaphysalis. 



Outer angle of second joint of palpi not acutely produced 6 



6. Palpi longer, second joint about twice as long as broad ; coxae IV of male 



not enlarged; tarsi II, III, and IV plainly divided, the basal part 



mucli shorter than the apical part (Amblyommini) AiiihJiiomma. 



Palpi shorter, second joint barely longer than broad; eoxa^ I^' of male 

 enlarged; tarsi II, III, and IV indistinctly divided, the parts subequal 

 in length (Dermacentorini) Dermaccntor. 



Genus CERATIXODES Neumann. 



Venter showing furrows as in Ixodes. Capitulum not produced 

 anteriorly in the middle, but the sides somewhat angulate; porose 

 areas oval, transverse. Palpi short, third joint no longer than broad, 

 and broadly rounded. Shield unmarked, no ocelli. Coxa I close to 

 rostrum, barely toothed behind ; coxa IV of male not enlarged. Pos- 

 terior margin of body without festoons. Stigmal plate circular. 



