134 
R. S. BAGNALL 
(in an unnamed African species) two bladelike process, which he calls 
«palettes», proceeding from a similar base as the ordinary hairs, one 
on each side of the ventral midline, 1 and a similar organ is present in 
Maerothrips Bagnall. 
In Urothrips we find six long hairs, each spi inging from a 
somewhat stout basal-part, and having no shorter bristles between them. 
In the mid-line, on the dorsal as well as the ventral side, there is a 
minute stalk, produced into a kind of inflated structure bearing at its 
extremity an extremely minute hair (PL III. flg. 13 x), but whether this 
structure is flat and plate-like, globular, or even vesicular, I cannot 
say. The six terminal hairs are thereby divided at their bases into two 
groups of three each. 
Sexual differences. 
The sexual characters of Urothrips, apart from the genitalia, the 
structure of which I have been unable to distinguish, are also peculiar 
to the genus, and have already been touched upon. The chief difference 
lies in the form of the terminal hairs, which are whip-like in the male 
and simple in the female, whilst the latter sex possesses a very minute 
tooth at each posterior angle of the prothorax (PL III. flg. 2), which 
cannot be distinguished in the male. 
Tracheal stigmata . 2 
In all the known Thysanoptera either three or four pairs of 
stigmata are present. They appear always at the anterior angles of the 
mesothorax, and on the sides of the first and eighth abdominal segments, 
whilst the fourth pair, which is invariable present in the Tubuliferct 
and as a rule, in the Terebrantia, is to be found on the metathorax, 
near its juncture with the mesothorax and close behind the attachment 
of the hind wings, when present. 
1 Trentuna specie di Tisanotteri italiani. (Atti Soc. Tose, di Sci. Nat., Mero., 
XXIII., pp, 77, plates V—VI., figs. I—8. 1907.) 
Alcune Notizie anatomiche sui Tisanotteri Tubuliferi. (Redia IV, fase. 2°, 
p. 369—381., figs. 1—17., July lütli 1908.) 
2 Karl Jordan, Anatomie und Biologie der Physapoda. (Zeitschrift für 
wissenschaftliche Zoologie. XL VII., 4., p. 541—620., tab. XXXVI—XXXVIII., 
Leipzig 1888.) 
H. Uzel, Monographie der Ordnung Thysanoptera, Königgrätz 1895. 
W. E. Hinds, Contribution to a monograph of the Insects of the order 
Thysanoptera inhabiting North America. (Proc. U. S. Nat. Mus. XXVI., p. 79—242., 
plates I—IX., No. 1310., Washington 1902.) 
