140 DR. J. BRAXTON HICKS ON UNDESCR1BED SENSORY ORGANS IN INSECTS. 
to draw attention to another somewhat similar group of organs observed about the joint of 
the trochanter and femur, chiefly on the former, and which I have found in all the insects 
I have examined. 
The organs in question consist, as in the structures above described, of a thin delicate 
membrane, probably the cuticle, stretching over, and closing in from the air, a tubular 
aperture in the chitine-layer of the part. This aperture may be circular or oval, the tube 
varying in length according to the thickness of the integument, curved as in the Hornet, 
or forming a globular cavity as in Silpha. The delicate membrane which covers over this 
aperture is generally level, sometimes having a ridge or a minute papilla in its centre, as 
in Meloe (PL XVIII. fig. G). 
In some rare instances, as in Formica rufa (PI. XVIII. fig. M), I have found that a few 
occur about the next joint (the tar so-femoral) . 
The following are those which I have selected to exemplify these structures : 
They are remarkably well shown in the genus Hippobosca. Pig. C, 1, represents the 
trochanter-femoral j oint of S. Mrundinis. The organs are found on both sides of the 
limb, and occur in groups of one or two rows of vesicles, each of which has a diameter of 
inch, the rows being either straight or curved. 
Pig. C, 2, shows those of H. Ovis ; they are rather more numerous than in H. Mrun- 
dinis, and of the same diameter. 
Those of H. equina are similar. 
Those of Musca domestica are represented at fig. D. In all the Diptera I have exa- 
mined they are alike; they are concentrated into a group of about ten to twelve on 
the femoral portion of the joint. The diameter of each is -^fa inch. 
In Fulex these organs can be seen, of a small size, about three in number, on the concave 
side of the trochanter. They are best shown in the Swallow-Plea. 
In Silpha (PI. XVIII. fig. E) they are well marked, being about eight on one side of 
the trochanter and six on the other, the centre of the tube being of much greater diameter 
than either the covering-in membrane or the internal opening, thus being of a globose 
form. The diameter of the covering-in membrane of the largest is yyVo inch. 
In the female of Lampyris noctiluca (Glow-worm) (PI. XVIII. fig. P) they are found 
in a row of six to eight, extending transversely across the trochanter on each side. The 
branches of the nerve proceeding to them can be plainly seen (fig. P, 1 c). 
In Meloe I have found these organs on the femur, close to the trochanter ; they 
are about twenty in number; the covering-in membrane has a central prominence 
(PI. XVIII. fig. G, 2 b, 3 b), on which the branch of the nerve (fig. G, 1 a, 3 a) ends, after 
passing up the tube in the integument. The diameter of this covering-in membrane is 
about 1^0 inch ; that of the papilla is 7-5V0 inch, whilst that of the nerve is still smaller. 
In Forficula auricularis (PI. XVIII. fig. H) they are found on each side of the tro- 
chanter, near the joint, on one side rather scattered and large, and on the other in 
a group of about six or seven. They are oval in form, and rather prolonged at one end. 
The diameter of the longest is y^o inch. 
These structures are found in the Grasshoppers (Tetrix) on both trochanter and femur, 
as shown in PL XVIII. fig. I, 3 ; they are oval, and in the common Grasshopper mea- 
