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regard as sexual; thus in the one sex, which we have described as 
the female, we find a minute tooth or papilla at each hind angle 
of the prothorax, which does not appear to be present in the other 
specimen, whilst the long terminal hairs of this latter specimen 
(which we regard as the male) are whip-like, being uniformly 
thick for about one-third their length, and then abruptly reduced 
and continued as a long colorless filament; whereas in the female 
these long bristles or hairs are gradually and evenly tapered from 
the base to the extreme apex. These characteristics have not been 
described in any known Thrips; and in this latter connection it is 
worth noting that the tube is encircled by six terminal hairs, but 
that there are no intermediate minor seta as in the Zubulifera 
known to us, though on the mid-line both dorsally and ventrally 
there is a specialized and very small seta, which divides the six 
terminal hairs into two lateral groups of three each. 
From the above lines it will be seen that Urothrips is charac- 
terised very strongly morphologically, and it is difficult to realize 
the importance of the various features in which this type departs 
from other ZAysaroptera, but to us it seems that a study of this 
Insect, and of other allied forms which we understand have recently 
been discovered, will cause a change in our present views as to the 
ancestry or phylogeny of the Zhysanoptera and their relationship 
with other groups. 
Without venturing any fixed or decided opinion it might be well 
to review some of these peculiar features. 
The structure of the antenna, of the sternum, and of the eleventh 
abdominal segment (or end of tube), the presence of the abdomi- 
nal papille, and the diminished or obsolete chætotaxy are difficult 
features to place in their proper perspective, in viewing the rela- 
tionship of Urothrips with others of the order, and, as we have 
already said, we can make no deductions from the primary sex 
characters, as we have been unable to describe the genitalia ot 
either sex, and because of this want of knowledge it is very poss- 
ible that the remarks and deductions we make under the various 
headings hereafter may be of less value than we at present think. 
Though we make the « Stigmata » our last heading, we believe that 
the number of stigmata is one of the most important features we 
have been able to bring forward, and that in this feature we may 
ultimately find the key to the puzzling questions that have arisen 
since the discovery of Urothrips. 
