296 Genus Ixodes 



Ixodes ricinus. 



Commencing with the adult stages : males and females are both 

 present upon the host, and they are frequently found thereon in copula- 

 tion. Pairing may, however, take place before the sexes have attached 

 themselves to a host ; this has as yet only been observed in unfed adults 

 in captivity. A female may pair with several males in succession. 

 The males, which are relatively scarce, remain attached to the host only 

 for a few hours and if they feed they can do so but moderately, their 

 external structures not permitting more than a limited amount of 

 distention. The males wander about the host in search of females 

 during the intervals when they are not feeding 1 . The females, on the 

 other hand, after having attached themselves to a host, remain in situ 

 hanging on by their mouthparts for 7-14 days and possibly longer in 

 cold weather. During this time the females are sought by the males 

 and gradually grow in size owing to the distention of their bodies with 

 blood derived from the host. Shortly before they abandon the host they 

 swell rapidly and attain their maximum degree of distention. Females 

 in all degrees of distention are found coupled with males. At times, 

 one or more additional males may be observed about the female whilst 

 one male has its mouthparts fixed in the vulva. It would appear as if 

 the other males were waiting their turn to enter into copulation. We 

 shall presently describe the process of copulation more fully. 



The fertilized and fully gorged female now releases herself from the 

 host and falls to the ground 2 . I have frequently observed females 



1 Although I. ricinus <r may attacli itself to a host it has not as yet been demon- 

 strated that it actually sucks blood for there is no record of the intestinal contents having 

 been examined after a male has detached itself from the host. It is conceivable that the 

 attachment may be mechanical, but the matter requires further investigation. It appears 

 worth noting here that we have seen males of Hyalomma syriacum bury their mouthparts 

 deeply into a cork whilst confined in a bottle after their removal from a tortoise. 



2 That the dropping of gorged females from the host may be influenced by temperature 

 was once observed to a remarkable degree when experimenting with Boophilus decoloratus 

 which was being raised by me in Cambridge. A cow infested with this tick, many females 

 being replete, was taken out of the warmed experimental stall into the cool air of a courtyard. 

 The females immediately began dropping off and " rattled like peas " on the ground. In 

 nature it is a common matter to pick up ticks along the paths pursued by cattle or game, 

 and this observation on Boophilus suggests a possible explanation why these paths should 

 at times be particularly infested, for it is along them that animals like cattle frequently 

 return from pasture in the cool of the evening. In nature, the female will at most wander 

 a foot or two from the path pursued by the host from which she fell, and will lay her eggs 

 at the foot of the vegetation bordering the path. The offspring would, therefore be 

 literally "put in the way of finding their food." 



