IDENTIFICATION OF TICKS 633 



To identify any species of tick the worker must first be able to 

 recognize the genus to which it belongs, and it may be of help before 



leaving the subject to emphasize some of the points 



... . , Salient points in the 



which are important in this connection ; it is not neces- identification of Ticks 



sary however, that the worker should be able to 

 name the tick with which he is experimenting, provided that he is able 

 to place it in its proper genus and to be certain that he is dealing with 

 one species only ; the species can be determined later by an expert. 

 When examining a specimen it is first necessary to decide whether it 

 is an adult or not; the immature stages of Argas and Ornithodorus, for 

 example, closely resemble the adults, more particularly the males, but 

 they can be distinguished from them at once by noting the condition 

 of the genital opening, which is entirel)* absent in the young stages, but 

 patent in the adults. In the subfamily Ixodinae all the females have 

 porose areas on the dorsal surface of the capitulum, and if these are 

 absent the specimen is either a male or a nymph. 



The genera of the Ixodini are apt to cause some confusion. It will 

 be seen from the table on page 632 that they fall into two main groups, 

 according as to whether the anal groove contours the anus in front or 

 behind ; in the case of many replete females it may not be very apparent, 

 and in this case it is best to examine an unfed tick. Of the three genera 

 included in the first group, Eschatocephalus and Ceratixodes contain only 

 somewhat rare species, and need not be considered further ; the charac- 

 ters mentioned on page 590 will serve to define the genus Ixodes. 



If the anal groove contours the anus posteriorly the tick may belong 

 to one of seven genera. The capitulum provides the next determining 

 character. If it is relatively short in proportion to the rest of the body, 

 the specimen belongs to one of four genera, Dermacentor, Rhipicephalus, 

 Margaropus or Haemaphysalis ; if it is long, to one of three, Hyalomma, 

 Amblyomma or Aponomma. Of the first group of four, Dennacentor is 

 distinguished by the rectangular shape of the basis capituli, b}* having 

 the second segment of the palp about as broad as long, by the ornament- 

 ed scutum, and by the presence of eyes, and if the specimen is a male 

 coxa IV will be larger than the others, though this is not a reliable charac- 

 ter. In Rhipicephahis and Margaropus the basis capituli is rectangular, 

 and has projecting sides ; in the former the palps have no transverse 

 ridges, and the spiracle is as a rule comma-shaped, while in the latter 

 there are short ridges on the second and third segments of the palps, and 

 the spiracle is circular or nearly so in both sexes.* 



* It should be remembered that the shape of the spiracle may differ in the two sexes. 



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