634 MEDICAL ENTOMOLOGY 



Haemaphysalis is distinguished from the other genera by having the 

 base of the second segment of the palp, always wider than the basis 

 capituli, and by the absence of eyes. Of the second group of three genera, 

 Hyahmma and Amblyomma are not easy to separate from one another ; in 

 the former the eyes are button-shaped, at least in Hyalomma aegyptinm, 

 and project from the pits in which they lie in a very characteristic man- 

 ner in both sexes, and the second and third segments of the palps are about 

 the same length. In Amblyomma the eyes are flatter and do not project 

 to any marked extent, and the second segment of the palp is longer than 

 the third. The species of Aponomma, which are mainly parasitic on 

 reptiles, have broad flat bodies, and are always without eyes. 



BREEDING AND MANIPULATION OF TICKS FOR 

 EXPERIMENTAL PURPOSES 



Success in the breeding and manipulation of ticks depends to a large 

 extent on an accurate knowledge of their life histories, the habits of the 

 early stages, and on the methods suitable for keeping their hosts in 

 captivity. When these are known the technique in most cases is simple, 

 and all the apparatus which is necessary is easily obtained. 



In view of the great variations which are found in the life histories of 

 the ticks of the different genera, it will be convenient to consider each 

 genus separately, and in doing so to recapitulate briefly the main features 

 of the life cycles in their relations to the technique which has to be 

 adopted to meet the case. The types of life cycles which are found in 

 each genus have been indicated in the foregoing descriptions. The life 

 history of every tick consists of four stages, the egg, the larva (charac- 

 terized by the possession of six legs), the nymph and the adult, male or 

 female ; there is in reality also a fifth stage, for the adults are not func- 

 tionally mature for a varying period after their emergence from the 

 nymphal stage. The nymph can always be distinguished from the adult 

 by the fact that the genital opening is not patent. All these stages are 

 as a rule blood-suckers ; there are however, a few exceptions as already 

 noted. 



The variations which exist in the life cycles depend upon the relations 

 of the several stages to the host, and it is evident that a great variety of 

 types is conceivable. The entire life from egg to adult may be completed 

 on one species of animal as host, or the succeeding stages may feed 

 on other species. The early stages may remain attached to the host 

 while they pass through the metamorphosis, or the}- may drop off 



