SCIENCE- G OSSIP. 



37 



CLASSIFICATION OF BRITISH TICKS. 



By Edward G. Wheler. 



(Continued from page 12.) 



Note. — Through a misunderstanding the block 

 inserted in the last number (fig. 3) represented the 

 underside of Argas persicns, instead of A. reflexus, 

 female. A correct fig. 3 is herewith substituted. 



Fig. 3. Argas reflexus. Female: 



The word " only " should be deleted in line 16 of 

 p. 12. The Argas has been found elsewhere in 

 Britain. 



II.— IXODINAE. 



FT1HE Ixodinae have the rostrum terminal, and 

 -*- never concealed under the body. Palpi four- 

 jointed, of which the fourth is very short, and is 

 situated in a hollow at the end of the third. Legs 

 somewhat unequal in length. They are six-jointed, 

 with two false joints, giving the appearance of 

 having eight joints ; one being on the femur and 

 the other on the tarsus of each leg ; but the latter is 

 absent on the front pair. The cuticle of the body 

 is very distensible in all stages, except in the case 

 of adult males, and covered more or less, according 

 to the state of distension at the time, by a dorsal 

 shield, or scutellum. This shield seldom or never 

 covers so much as one half of the body, and as dis- 

 tension takes place it is proportionately less. In 

 the case of males, which do not distend, it is 

 entirely covered, or with the exception of only a 

 narrow margin. Stigmata are encircled by peri- 

 tremes situated behind the haunches of the fourth 



pair of legs. The sexual orifice is situated beneath, 

 between the haunches of the first three pairs of 

 legs. In the males of the genus Ixodes it is only 

 rudimentary or obsolete, sexual intercourse being 

 effected by the rostrum. The orifice is half en- 

 circled by a groove, opening outwards behind. 

 There is considerable difference between the sexes, 

 the males being usually the smaller. There are 

 often eleven indentations on the posterior margin. 

 The dorsal base of the rostrum of the female has 

 two symmetrical hollows, with numerous punctua- 

 tions, which are not found in the males, nymphs, 

 or larvae ; their purpose is doubtful. 



The Ixodinae are chiefly parasitical on mammals, 

 but also attack birds and reptiles. They rarely 

 confine themselves to one species of host. 



The genera of the sub-family of Ixodinae are : — 



Ixodae, comprising Ixodes, Haemalastor, Apo- 

 nomma, Hyallomma, Amblyomma. 



Rhipicephalae, comprising Rhipicephalus, Hae- 

 maphysalis, Dermaeentor. 



Ixodae. 



The Ixodae are distinguished from the Rhipi- 

 cephalae by the length of the rostrum, which 

 reaches nearly to the end of the palpi, sometimes 

 further. The palpi are longer than broad. The 

 presence or absence of eyes divides the genus into 

 two groups : — Amblyomma and Hyalomma have 

 eyes, which are placed on the marginal edge of 

 the shield (fig. 5). Ixodes, Haemalastor, and 

 Aponomma have not any eyes. 



Fig. 5. 



The form of the anal groove gives another 

 division. In Ixodes and Haemalastor this groove 

 contours the anus in front and opens behind 



