THE PLUME-MOTHS OF CEYLON. L51 



last genus exhibit remarkable differences inter se, especially in the 

 structure of the palpi, but the group is small, compact, and well 

 characterized, so that it appears undesirable to split it up in the light 

 of our present knowledge. In the presence of the peculiar costal 

 scale-tufts and in the well-developed maxillary palpi, 0. trachyplera 

 amongst our species in Ceylon seems remote in structural characters 

 from the other members of the genus, but, as stated above, it 

 does not appear necessary at present to separate it generically. 

 0. microscopica is also very distinct from the remaining species 

 by the shallowness of the first cleft in the forewing and the very stout 

 sixth segment in the hindwing. 



Distribution in Space and Time. 



It is especially noteworthy that nearly all the species of Orneodida; 

 hitherto discovered in Ceylon are peculiar to the Island, the mono- 

 typical genus Trisccedecia being indeed unknown outside of Ceylon. 

 With an increase of our knowledge of the Asiatic forms of this group, 

 it is possible that our views regarding their geographical distribution 

 may require considerable modification, but in the light of what we 

 know at present it is perhaps permissible to deduce a very high 

 antiquity for this little family, such deduction being based logically 

 on the one hand upon the extremely similar but highly peculiar 

 f acies of the members of this group , and on the other hand upon their 

 extremely wide distribution throughout all the zoogeographical 

 regions,* whilst the occurrence of the individual species within very 

 circumscribed areas appears to indicate very limited powers of distri- 

 bution. Except in the case of 0. hexadactyla, which occurs through- 

 out the Holarctic realm (i.e., Europe, N. Asia, and N. America), 

 we know no single instance of an Orneodid species whose distribution 

 extends outside of a very small portion of one of the zoogeographical 

 regions, a state of affairs which appears to point to the fact that 

 these localized species have been evolved within very circumscribed 

 areas of space, although the universal distribution of the family 

 forbids us to add the qualification " and of time also." Nothing is 

 known of any Orneodidse in a fossil state. 



Habits and Life-Histories. 



So far as Ceylon is concerned it is a matter for regret that, up to 

 the present at least, the information under this heading is almost 

 a perfect blank. The few specimens of imagines collected have 

 almost invariably been attracted by light, a method of capture which 

 gives us very little information about their habits in a natural state. 

 I once, however, beat a specimen of 0. montigena at Ohiya, and this 

 was disturbed from a mossy roadside bank, on which it settled again. 



* No Orneodid has been recorded as yet from New Zealand, although it is 

 reasonable to expect that some species will be found there. The members of 

 this group are, however, rather inhabitants of warm climates. 



