IXODID.E : SYNOPSIS OF GENERA 363 



The Ixodina have the legs unequal, of six segments with two 

 false segments, making them look as if composed of eight segments. 

 The rostrum is terminal and never hidden beneath the body. The 

 sexual orifice is situated between the haunches of the first three 

 pairs of legs. In the males the orifice is obsolete or very rudi- 

 mentary ; sexual intercourse being effected by the rostrum. The 

 males are smaller than the females. The shield in the females never 

 covers so much as one half of the body even when fasting, also 

 in the larvae and nymphs ; but in the males, which do not distend, 

 the shield covers the body entirely, or all but a narrow margin. 

 The Ixodinae are divided into two groups : (i) the Ixo&ce .and (2) the 

 Rhipicephalce. The former have a long proboscis reaching nearly to 

 the end of the palpi or even a little longer than the palpi. The 

 palpi are longer than broad. The Rhipicephalcz have short palpi, 

 nearly or quite as broad as long, more or less conical or subtriangular. 

 They were called Conipalpi by Canestrini. 



SYNOPSIS OF GENERA. 



A. Rostrum concealed in adult, partly exposed in larvae and 



nymphs. No dorsal and ventral shields. 



Body flat with thin edges, finely shagreened and punctate . Argas. 

 Body with numerous small round granules and with thick 



sides Ornithodorus. 



B. Rostrum terminal. Body with dorsal shield over some 



part of it. 



I. Rostrum and palpi longer than broad (Ixodince}. 



a. A groove around anus in front. Palpi caniculated in 



both sexes . . . . Ixodes. 



Palpi claviform, not caniculated in the male ; legs 

 very long Escatocephahis . 



Palpi claviform, not caniculated in the male ; anal 



groove absent in the female Ceratixodes. 



j8. A groove around the anus behind. 



No eyes ; ad -anal shields Aponomma. 



Eyes present. 



Males with no ad-anal shields Amblyomma. 



Males with ad-anal shields Hyalomma 



II. Labium and palpi short ; palpi not, or very little, longer 



than broad (Rhipicephala) . 

 a. No eyes. 



Rostrum rectangular ; no ventral shields in the male . H&maphysalis. 

 0. Eyes present. 



Rostrum with salient angles ; either two or four 



shields at the side of the anus in the male . . . Rhipicephalus. 

 Rostrum rectangular. No ad-anal shields in the male, 

 but usually with greatly-developed coxae on fourth 

 pair of legs Dermacentor. 



