ARTHROPODA 177 



the adult male and female tick. The larvae are provided with six legs 

 and are without sexual opening or stigmata. The nymphs have eight 

 legs and are provided with stigmata, but are without sexual opening. 

 The sexually mature male and female ticks have eight legs, and are 

 provided with both stigmata and sexual openings. The number of 

 eggs deposited by the adult female is very large. As soon as the 

 larvae emerge they attach themselves to lizards, very small mammals 

 of widely different species, and birds. They suck the blood of their 

 hosts but do not appreciably increase in size. When they return to 

 the ground they slough their outer skin and enter upon the nymph 

 stage. The nymphs, like the larvae, remain for some time attached 

 to small mammals, and upon leaving their 

 host they enter upon the stage of sexual 

 maturity. The male arid female become 

 parasitic upon the larger vertebrae, where . 

 copulation takes place. The body of the 

 female becomes very much distended, partly 

 from the filling of the intestine with blood, 

 and partly as a result of the development of FlG 88 _ Ixodes ricinus 

 numerous eggs (fig. 88). She finally quits (L-)- Female, gorged with 



,, , , ., blood. Seen right, from the 



the host in order to deposit her eggs upon dorsal) left> from the ventral 

 the ground. Females which are very much surface, 2 : i. (After Pagen- 

 distended and are upon the point of laying 

 eggs are not good subjects for demonstration 

 purposes. 



Specimens are killed in alcohol, and this must be done under the 

 cover-glass, or the extremities will not be extended. They should be 

 viewed first with a magnifying glass or with a low power microscope. 

 The body is unsegmented and there is no external line of demarcation 

 between the cephalo-thorax and the abdomen. The legs are attached 

 to the ventral surface. In males and young females, the body is oval ; 

 in older females it is nearly oblong ; while in quite old females the 

 oval outline is resumed. The dorsal surface is arched, the ventral 

 surface plane, and it is customary to distinguish an anterior, a pos- 

 terior, and two lateral marginal edges. At the anterior end of the 

 body, immediately in front of the first pair of legs, is the capitulum, 

 or " false head/' which bears the mouth-parts. These consist of a 

 proboscis-like structure, flanked on either side by the palps. Upon 

 the dorsal surface, immediately behind the capitulum, is the arched 

 scutum or shield, in colour of a varying shade of brown. With the 

 exception of a narrow margin at the hinder end and at the sides, the 

 dorsal surface in the male is entirely covered by the scutum. In 

 the female, the scutum is much smaller and is of a different shape. 

 The difference in size is noticeable even in quite young females, and 

 12 



