[67] Adaptation of Ticks 345 



fact that many species of Ixodes are only known to science in their 

 female and immature stages, it would appear probable, if my theory 

 holds, that this is merely due to the males not having as yet been sought 

 for in the habitats of their hosts 1 . 



A great many males belonging to Haemaphysalis, Dermacentor, 

 Rhipicephalus, Amblyomma (and Aponomma) are known, these genera 

 of Ixodidae being rich in species. The males of Boophilus, Hyalomma, 

 Rhipicentor and Margaropus, of which there are few species, are likewise 

 known. In all of these genera the males are found close to the females 

 and attached to the host. These genera are chiefly parasitic on animals 

 with wandering habits, and the males of these genera do not exhibit 

 hypostomes which are markedly dissimilar to those of the females; 

 the hypostomes are well armed in both sexes. It is only in the genus 

 Ixodes that we find well-marked sexual dimorphism in respect to the 

 structure of the hypostome. 



1 As a further confirmation of the views here expressed, I would state that we 

 have recently (March, 1911) discovered a male of Ixodes hexagonus in the nest of a 

 hedgehog. This is the first male we have captured, whereas we possess hundreds of 

 females, nymphs and larvae found on various hosts. (The rarity of the male is rendered 

 evident by the fact that there is not a single specimen of a male in the Museums in 

 London, Paris and Berlin.) When the male was placed in a receptacle with an engorged 

 female from the same nest, copulation occurred after a few minutes and was repeated 

 several times. 



