IN THE ANTENNÆ OF INSECTS. 149 
the perforation of the inner wall. The last joint is plumose, exactly resembling the third ` 
joint of the seta in Musca, Mesembryum, Eristalis, Volucella, and other similar forms. 
` In Tipula (Tab. XXIX. fig. 4) these organs (precisely like those in Hippobosca, Bom- 
bylius, &e.) are to be found on the third joint of the antenna, which is more elongated 
and dilated than the rest, as is seen in fig. 4, a. Their diameter is 3257 inch. 
In Ctenophora the third joint is much more dilated, as at fig. 4, 6, c. In Ctenophora 
bimaculata (fig. 4, c) this dilatation is well marked on one side, and on this part these 
organs are readily observed, and the nerve distinctly seen to proceed to them, as in fig. 4, el. 
In Bibio Marci the antenna is composed of nine joints; the first two are free from any 
of the above appearances ; but the last seven all possess them on one side, and a nerve 
can be traced distinctly to them. . But the most remarkable condition of this antenna is, 
that from the third to the eighth inclusive, on the outer aspect of each joint is a cavity 
of considerable size, similar to those described in Mesembryum, the appearance of the 
floor being the same. The aperture leading to this cavity is about ybg inch diameter, 
and around its wall is a layer, apparently of tubuli, as around the chambered cavity of 
the Blow-fly, and to each of these a nerve can be very plainly seen to be given off from 
the antennal nerve as it passes by them. 
In this insect the advantages of the use of chlorine are strongly shown, the whole of 
it being of a jet-black, which in a day or two becomes quite colourless. 
The antenna of Asilus cristatus is very like that of Bombylius in shape and arrange- 
ment; the organs are, however, larger and more scanty. 
The club-shaped antenna of the Butterfly approaches that of the Blow-fly very closely, 
in possessing both the small transparent dots as well as the chambered cavities. I have 
figured the antenna of Argynnis paphia (Tab. XXIX. fig. 5). Both the above structures 
- extend nearly to the base of the antenna, but more sparingly towards the lower end. The 
small organs are surrounded by various cuticular markings, and vary from 3555 to 5565 
inch (fig. 5,51). The openings into the chambers are in diameter from 5355 to 1355 inch 
(fig. 5, 6 2, 2). The chambers of the cavity vary from two to six; in the centre of their 
- base is a projection or papilla, and the floor viewed from above presents the same ap- 
pearances as in the Blow-fly. 
I may remark that the small organs can be in no way mistaken for the roots of the 
scales, their form being very dissimilar. 
I have not carried out the examination in the antennz of Moths, but have found these 
small organs in the dilated extremity of the divisions of the antenna ‘of the Drinker Moth. 
In the Hymenopterous group we find these organs very extensively spread over the 
antenna, the external form varying somewhat in aspect; that of the Hive-bee (Apis 
mellifica) being a beautiful illustration, showing as it does the structure on a larger scale 
than any I have as yet described; and as the antenna is very free from cuticular markings, 
the nerve is very distinctly seen to give off a branch to the groups, which in this insect 
only occupy one side of the antenna (Tab. XXX. fig. 6). 
Each structure consists (viewed from above) of round transparent spots, about 1787 
inch diameter, but on a side view they are seen to be depressions of the surface, the internal 
“wall being perforated, with a very thin membrane closing in the perforation, which is 
