CLASSIFICATION OF TICKS 577 



dark brown chitin ; they lie ventro-laterally one on each side behind 

 coxa IV. In the Argatini they are situated between legs III and IV. 

 Each spiracle may be circular, oval, triangular or comma-shaped ; its 

 size, shape and structure is of importance in the separation of genera 

 and species. It is more fully described further on. 



CLASSIFICATION 



The classification of ticks has attracted the attention of many zoolo- 

 gists, and the literature of the subject is very extensive ; it is not possible 

 in a limited space to review it in detail, and only the main points are 

 given here. The worker will find a complete historical review of the 

 subject of the classification of ticks in the Monograph of the Ixodoidea, 

 Part II, by Nuttall in collaboration with Warburton, Cooper and 

 Robinson. 



According to Neumann ticks are placed in the family Ixodidae, which 

 is divided into two subfamilies, the Ixodinae and the Spelaeorhynchinae. 

 The subfamily Ixodinae contains two sections, the Ixodini and the 

 Argatini, and these are further sub-divided into several genera, containing 

 more than 200 species. The Argatini are widely separated from the 

 Ixodini, and there are no intermediate forms known at present. The 

 Argatini consists of a small number of specialized ticks which fall 

 naturally into two genera as described below. The Ixodini, on the other 

 hand, contains a large number of somewhat closely related species 

 all of which have a dorsal shield or scutum, which is absent in the 

 Argatini. 



Many attempts have been made to arrange the Ixodini in natural 

 groups. As a basis for the various methods of classification the relative 

 length of the palps has been mainly utilized, as being an external feature 

 which shows a difference in anatomical structure. Neumann has, however, 

 pointed out that it leaves too much to the judgment of the observer, and 

 also cuts across the real affinities existing between the various species. 

 In 1902 he suggested that the grooves on the ventral surface of the 

 Ixodini were good external features to select as a basis for classification ; 

 since then Banks and Warburton have independently drawn up systems 

 of classification depending on the position of the anal groove. 



Banks places ticks in the superfamily Ixodoidea, which he divides into 

 two families, Ixodidae and Argasidae ; the former he sub-divides as 

 follows : 

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