vi Preface 



imperfectly described ; we propose to retain them in this category until 

 they may have been properly described and shown to be valid by their 

 authors or other workers. We do not consider it justifiable, in the 

 present state of our knowledge, to found species on immature forms, a 

 proceeding which might be warranted if the immature forms of all 

 established species were known, whereas this is only true of 8 out of 51 

 species in the case of Ixodes. We agree in the main with Neumann in 

 the synonomies of species, both valid and condemned, but we have in 

 some instances arrived at different conclusions. Our lists of condemned 

 genera and species and of doubtful species, which have been compiled 

 by one of us (G. H. F. N.) with great labour, sufficiently demonstrate 

 the difficulties we have encountered in separating the wheat from the 

 chaff. These lists should at least prove useful to those desiring to 

 avoid the giving of already preoccupied names to new species of Ixodes. 

 Some of the synonyms must, from the nature of things, necessarily be 

 regarded as tentative. 



Of the innumerable species of Ixodes that have been described, we 

 are only able to recognize 51, and there may be but 48 which are valid. 

 As will be seen from the text, a number of species and their various 

 stages are adequately described and figured by us for the first time. 



The notes on Biology refer to matters of special interest relating to 

 some of the species. We have added thereto two appendices dealing 

 (I) with oviposition in Ornithodorus movhata, and (II) with the adaptation 

 of ticks to the habits of their hosts. The appendices are reprinted from 

 papers by Nuttall and Merriman and by Nuttall, which have recently 

 appeared in Parasitology, Vol. IV (1911), and which bear directly upon 

 the subject in hand. 



Illustrations. 



Curiously enough, some of the commonest species have never been 

 accurately figured before, or figured at all : we have endeavoured to 

 make good this deficiency. 



The 94 new illustrations in the text, like our earlier ones, are in most 

 cases reproduced from large drawings made from unmounted specimens 

 preserved in alcohol. The drawings were made with the aid of a 

 camera-lucida mounted on a Zeiss binocular microscope and used in 

 conjunction with a Zeiss drawing-board. A scale drawn to one side of 

 the figure usually indicates the magnification employed. Certain 

 highly magnified figures of the capitulum, hypostome and other structures 



