Ixodoidea. Ticks. 121 



KEY TO SPECIES OF GENUS DERMACENTOR. 



Scutum blackish, without white spots, in male pubescent. 

 Porto Rico. D. Nitens. 



Scutum nearly as broad as long : second palpal article with 

 dorsal retrogade spine in both sexes. Europe, America, Asia. 



D. Reticulatus. 



Body oval : hairs few. D. Eledus. 



Body oblong (in male triangular) hairy. D. Variegatus. 



I^ight spots on scutum (in male symmetrical) with one anterior, 

 large, arrow-shaped. Africa. D. Rhinocerotis 



Scutum with 3 spots (female) or 4, symmetrical (male). 

 Congo. D. Circumguttatus . 



Scutum glabrous in male and palpi extended laterally. Syria. 



D. Parvus. 

 Subfamily Ixodin^. 



Palpi long, usually about the same length as the hypostome. 

 Genera : Ixodes, Eschatocephalus , Aponomma, Amblyomma, and 

 Hyalomma. 



Genus Ixodbs. 



Kyes absent. Palpi long. Anal groove open, or closed caudad, 

 but tangent to the anus by its anterior concavity. Tarsi without 

 terminal spurs. Male with ventral shields ; pregenital shield be- 

 tween genital pore and capitulum : 2 lateral epimeral shields, 

 more or less surrounding the coxae and stigmata : a genito-anal 

 shield of elongate pentagonal form between genital pore and anus ; 

 an anal shield, triangular, ogival, or circular, caudad of preced- 

 ing, the anterior apex encircling the anus, the base formed by 

 the posterior margin of the body; two adanal quadrangular 

 shields parallel to the anal shield. Scutum leaving an uncovered 

 lateral and posterior margin ; postero-marginal festoons ab-sent. 

 Stigmata oval. 



Female. — With three dorsal longitudinal posterior grooves on 

 the ventral surface ; two long genital groves extending from the 

 vulva and diverging backward, and two anal grooves united in 

 front of the anus, parallel or divergent in back, rarely convergent. 

 Stigmata circular. 



KEY TO THE SPECIES OF THE GENUS IXODES. 



Female. — Porose areas broader than long and close together. 

 Male. — Scutum pubescent. I. Ricinus. 



