MR. J. 0. WESTWOOD ON NYCTERIBIA. 279 
term he also in like manner applies to the two protruded lateral organs of the mouth 
of the Hippoboscide. That these organs are perfectly analogous, Latreille had long ago 
implied by describing them both under the same dubious appellation, ‘‘ palpi?” As 
to their real analogies among the organs of a mandibulated mouth, I however offer 
no opinion, observing only that in defending the delicate central inferior spiculate ap- 
paratus of the mouth, they appear to perform the functions of the articulated sheath of 
the rostrum of the Hemiptera. This apparatus of the lower part of the mouth of Nyc- 
teribia consists at first sight of a large basal bulb-like organ, terminating in an elon- 
gated slender and horny style, precisely similar, in fact, to the same organ in Eippobosca. 
On each side of the base of the style, in the species under examination, there are two 
or three fine hairs as long as the style itself. The style in two individuals appeared to 
‘be composed of two demi-sheaths, although in the other specimen it formed only a single 
undivided canal, which from analogy with Hippobosca is evidently its real construction. 
It is not a simple organ, but contains, like its representative in Hippobosca, several sete. 
I found that it inclosed at least two sete, of equal length with the canal itself, one of 
which was more robust than the other; indeed in one specimen the more robust one 
appeared divisible into two sete, while in another this was not only the case, but the 
more slender one also presented the same appearance. Analogy, however, with Hip- 
pobosca would induce us to suppose that there are but two sete, as above described, 
inclosed in the canal. Latreille, quoting the observation of Hermann that he had not 
clearly observed the structure of the mouth, but had noticed four palpi, two short and 
thick, and two longer and more slender, excuses the supposed inaccuracy of that author 
on account of the minuteness of the animals. It is evident, however, from Hermann’s 
figures that the two short and thick organs were the antenne. 
The thorax exhibits a very remarkable structure. It is flat, and of a form somewhat 
between oval and round ; its upper surface is of a whitish coriaceous substance, divided 
into compartments by narrow crustaceous ridges. This structure was admirably de- 
scribed by Linnzus under the term ‘‘thorax angulatus cruciatus ;” notwithstanding 
which, Hermann, evidently judging from the inaccurate figures referred to by Linneus, 
conceived that the description was not intended by that author for an insect of this 
genus. ‘The inferior surface extends in a plate beneath the place of insertion of the 
legs, the femora of which are consequently prevented from being brought below the 
level of the under surface of the thorax, although they possess a considerable power of 
upward motion, this being effected by the soldering of the core and trochanters of the 
four hind legs with the dorsal region of the thorax, whereby, as Latreille observes, the 
back of the thorax, in fact, becomes the breast. On examining the anterior and su- 
perior extremity of the thorax, a minute raised line is seen to extend in a curved direc- 
tion on the outside of the base of the fore legs, immediately behind the place of in- 
-sertion of the head, somewhat in this shape, Gp. Taking, therefore, into consideration 
