THE PLUME-MOTHS OF CEYLON. 
151 
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, O. trachyptera 
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 fore wing and the very stout 
sixth segment in the hindwing. 
Distribution in Space and Time. 
It is especially noteworthy that nearly all the species of Orneodidse 
hitherto discovered in Ceylon are peculiar to the Island, the mono- 
typical genus Trisecedecia 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 
facies 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. 
