TYPES OF LIFE HISTORIES OF TICKS 635 



when replete with blood, remaining concealed apart from the host until 

 they have digested the meal and passed on to the next stage ; only one 

 feed may be taken, or several, and in many of the Argatini the female 

 may feed more than once between each act of oviposition. Copulation 

 usually takes place on the skin of the host, the smaller and more active 

 male seeking out the female, though in rare cases, such as that of 

 Amblyomma hebraeum, the female searches for the male. The proportion 

 of the life of the adult stages which is passed on the skin of the host 

 varies considerably ; in most of the genera of the Ixodini the females fill 

 up with blood in a comparatively short time, but in Aponomma they 

 ma}- remain attached to the host for a long period, often extending to 

 months. It must not therefore be supposed that all ticks which are 

 firmly attached to their host are in the act of feeding, for this is not 

 necessarily the case ; they may remain attached for a considerable time 

 without any appreciable increase in size, and then become distended in 

 an hour or so ; this is commonly seen in the case of Aponomma gervaisi. 



The types of life history which are met with may be conveniently 

 grouped into four classes as follows : 



CLASS 1. Ticks the larvae of which feed on one species of animal, or on 

 a group of related animals ; the adults, and to a certain extent the nymphs 

 also, may feed on many different kinds of animals but as a rule not on 

 the species which serves as host for the larva ; both the larvae and 

 nymphs always drop off to undergo the metamorphosis, after which they 

 become attached to another individual. Hyalomma aegyptium is a good 

 example of this type ; its larvae will only attach themselves to some 

 small mammal, never to the species of host on which the adults are 

 found. According to Donitz the larvae may feed on some particular 

 bird or group of birds (hawks). Rhipicephalus simus and R. capensis, as 

 shown by Lounsbury's experiments, also conform to this type, for though 

 the adults and nymphs are found on most farm animals the larvae will 

 not feed on them. 



CLASS 2. Ticks the larvae, nymphs and adults of which feed either on 

 one particular group of animals (Reptilia, Leporidae, etc.), or indiscrimi- 

 nately on a great variety of animals. The majority of ticks belong to this 

 class. The first type is exemplified by the ticks of the genus Aponomma 

 and by some species of Haemaphysalis. A. gervaisi for instance occurs 

 in all its stages on many species of snakes and lizards, but has never been 

 taken from a mammal. Haemaphysalis leporis has adapted itself to the 

 habits of the Leporidae and is rarely found on other hosts. Haemaphy- 

 salis bispinosa is a good example of the second and commonest type ; it 



