9(3 
Mallophaga 
no doubt that the sub-genus Aptericola is merely a group within the 
genus Rallicola, conveniently distinguished by its robust form. Rallicola 
is, as I have stated above, confined to rails, and found upon all sorts 
and sizes of rails over the length and breadth of the globe; and I have 
reasons, partly stated above, for considering it a somewhat primitive 
Ischnoceran genus, certainly more primitive than Philopterus and 
Degeeriella, which appear to have developed from the same branch of 
the original stock. 
Only one other Mallophagan genus, Pseudomenopon, is found solely 
upon rails, and is generally distributed amongst them. This is, so far, 
monotypic, but will probably be found to contain a number of species 
when it is critically examined, as has been the case with other genera 
(e.g. Docoplioroides and Giebelia). I have not succeeded in finding 
Pseudomenopon upon Apteryx. A few species of Lipeurus, PhilojMrus, 
Degeeriella, and one of Laeniobothrium are also found upon rails, but 
these would seem to be comparatively late acquisitions, as they are not 
generally distributed, and have chiefly been found upon Fulica, 
Gallinula, and PorjAiyrio. 
The robust form of the species of Rallicola from Apteryx may also 
possess some significance. In general, large Mallophaga are found upon 
large birds. This is not by any means always true. If it were, we 
should expect to find the largest Mallophagan species upon the ostrich, 
whereas it occurs upon a condor. Similarly Ricinus, which comprises 
fairly large species, is found chiefly upon small passerine birds. But, 
in general, when a genus is well distributed over a considerable number 
of nearly related hosts, the size of the parasite is roughly proportional 
to the size of the host. Thus species of Lipeurus found upon albatrosses 
are larger than those found upon the larger petrels; and these in their 
turn exceed in size those found upon the little storm petrels. The 
largest species of Pliilopteims are found upon ibis, storks, and vultures; 
of Colpoceplialum on storks, cranes, hornbills, etc.; of Goniodes upon 
peafowl and tragopans; and many similar instances might be quoted. 
Arguing on general grounds, then, I should, had these species of 
Aptericola been submitted to me without any data as to the host, have 
given the opinion that they came from a group of large ralline birds. 
But no species of Apteryx is very large, and certain of them are smaller, 
bulk for bulk, than some of the larger rails, as, for instance, some 
species of Ocydromus, which carry Rallicola of the ordinary small type. 
A possible inference is that Apteryx is an offshoot of a larger- 
statured stock. Since it is generally agreed that the Apterygidae and 
