342 Appendix II [64] 



On the structure of the hypostome in £ Ixodes. 



There are 18 species of Ixodes of which the males and females are 

 known. About one of these (pratti, Banks) we have no information 

 such as we require for this discussion. Of the 17 remaining species, 

 the sexes have been found together upon the host in 13 (I (a) and (&)), 

 and in 4 (II) only the females have been found upon the host: 



I (a). In six the sexes have been found in copula upon the host, 

 namely,' ricinus, rasus, ugandanus, schilling si, pilosus and boliviensis. 

 The hypostomes in the males of the first five species are characterised 

 by prominent basal teeth; boliviensis has a well-armed hypostome. 



I (b). In seven species (cavipalpus, rubicundus, minor, Icricatus, 

 tenuirostris, angustus and holocyclus) both sexes have been found upon 

 the host, but there is no specific mention of their having been found 

 in copula. The hypostomes of the first two species possess prominent 

 basal teeth ; minor, loricatus and tenuirostris possess hypostomes which 

 are well armed with pointed teeth ; in angustus and holocyclus the 

 hypostome is only moderately armed. 



II. In four species (hexagonus, canisuga, putus and vespertilionis) 

 there is no record of the males having been found upon the host. In 

 the first two the hypostome is but moderately armed, whereas in putus 

 and vespertilionis it is almost unarmed. 



The structure of the male mouthparts, therefore, bears a direct 

 relation to the presence or absence of the male upon the host and the 

 occurrence of the sexes in copula upon the host. Of the six species 

 (I («)) which have been found in copula upon the host no less than 

 five possess hypostomes with prominent basal teeth. It is probable that 

 some of the species placed in the following division (I (&)) will yet be 

 found in copula when they have been more carefully observed. In 

 Group I (a) and (b) there are 13 species enumerated in only two of which 

 the hypostome may be described as moderately armed. In Group II, 

 regarding which there is no record of the males having been found upon 

 the host, the male hypostome is but slightly armed in two and prac- 

 tically unarmed in two species. 



