401 



moreover, Mallophaga make use of Hypohoscidœ for transport- 

 ation from one bird to the other." 



E. Jacobson will this time endeavour to supplement this 

 interesting account by trying to obtain the bat which frequents 

 the cave and by making further observations on the habits of 

 Arixenia. 



Although Jacobson's specimens very closely resemble ^na:g«za 

 esaii in faciès, a cursory examination convinced us at once that 

 they represented a different species, which has since been 

 described as 



Arixenia jacohsoni Burr (1912). 



The species is easily distinguished from A. esan Jord. (1909) 

 by the pro- and mesonotum being truncate posteriorly 

 instead of being rounded, and by the greater length of the 

 thoracical sterna, both in the adult and immature individuals. 

 These external distinctions are not very trenchant and, con- 

 sidering that the species of insects inhabiting the Malayan coun- 

 tries are as a rule split up into a number of geographical races, 

 would hardly justify a specific separation of jacohsoni from esan. 

 However, a closer examination of the morphology and anatomy 

 has revealed so many differences that the two forms must be 

 considered as distinct species. 



The discovery of adult specimens has enabled us to fill the 

 lacunae in our knowledge of the general build of Arixenia, the 

 main point being this, that the adult examples do not essen- 

 tially differ from the immature stages, apart from the size, 

 the reproductive organs, and the antennie. The details of the 

 morphology and anatomy which Jordan has published of the 

 immature Arixenia esan, therefore, may be accepted as applying 

 on the whole also to the still unknown imago of that species. 

 On the other hand, the description of the mouth-parts, gut, and 

 some other organs of A. csau does by no means fit A. jacohsoni, 

 the divergency between the two species being greater than one 

 would expect from the close agreement in external features. 



Head. 



The head of Arixenia öfters an interesting mixture of typical 

 Earwig characteristics and of peculiarities restricted to this 

 51 



