362 THE ANIMAL PARASITES OF MAN 



colour and regain the host afresh ; the female gradually swells until 

 she attains that large inflated form so characteristic of ticks. The 

 male does not swell, but nevertheless feeds upon the host and 

 fertilises the female. 



The act of coitus is strange, the male tick inserts its rostrum and 

 other mouth organs into the sexual orifice of the female, between the 

 base of the posterior pair of legs. The males then die and the females 

 fall to the ground and deposit the ova. There are variations in the 

 different species, of course, from those given above, which apply 

 solely to Ixodes reduvius. The larvae and nymphs seem to attack 

 most animals, but the adults mainly keep to the same host. The 

 periods in the life cycle of ticks not only vary in the different 

 species but in each species according to climatic conditions. For 

 instance, in the Bont tick (Amblyomma hebr&um, Koch), Lounsbury 

 has shown that the development is rapid in summer, slow in winter. 

 The period from the time that the female drops to the time she 

 commences to lay eggs varied in specimens observed by him from 

 twelve days in summer to twelve weeks in winter, and the complete 

 period from the dropping of the female to the hatching of the eggs, 

 from eleven weeks in summer to thirty-six weeks through the winter. 

 Other stages vary in a similar manner. 



Ticks may live a long time away from the host provided they are 

 supplied with a certain amount of moisture. Mr. Wheler kept dog 

 ticks (Ixodes plumbeus) in the larval stage for ten months. The 

 pupae, male and female, of Ixodes rqduvius for six months. 



In many species moulting takes place off the host, but in Ixodes 

 bovis, now known as Rhipicephalus annulatus, Say (the carrier of 

 Texas fever), moulting takes place on the host, and in many other 

 species also. 1 Some species of ticks leave their host on its death 

 (as the dog tick, Hcemaphysalis Leachi), but others die with the 

 host (Bont Tick, Amblyomma hebrceum). 



CLASSIFICATION OF IXODID^:. 



The TICKS, or Ixodidce, are divided into two groups, known as 

 (i) Argasinae, (2) Ixodinae. The Argasince are told from the Ixodinae 

 by the absence of dorsal or ventral shields in both sexes, and also 

 by the rostrum being placed beneath the cephalo-thorax, which 

 covers it over, except in the larval stage, in which it is terminal, and 

 in the pupal, when it partly projects. Legs nearly equal in length. 

 The sexual orifice is situated between the two first pairs of legs. 

 The males usually smaller than the females. 



1 Some Ticks require only one (R. decolor atus] others two (R. evertsi) and some 

 three hoats (R. appendiculatus) in order to reach maturity. 



