IN THE ANTENNAE 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, Volticella, and other similar forms. 



In T'qiula (Tab. XXIX. fig. 4) these organs (precisely like those in Hippobosca, Bom- 

 bylius, &c.) are to be found on the thii-d joint of the antenna, which is more elongated 

 and dilated than the rest, as is seen in fig. 4, a. Their diameter is -axoo inch. 



In Ctenophora the third joint is much more dilated, as at fig. 4, b, c. In Ctenophora 

 bimaculata (fig. i, 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 tig. 4, e 1. 



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 aU 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 tliird 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 -^^ 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 cristatits is very Kke 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, hut more sparingly towards the lower end. The 

 small organs are surrounded by various cutieular markings, and vary from 50^00 to tchrj 

 inch (fig. 5, b 1). The openings into the chambers are in diameter from -jaVo to j-s^nj inch 

 (fig. 6, 6 2, 2). The chambers of the cavity vary from two to six; in the centre of their 

 base is a projection or papiUa, 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 br>ing very dissimilar. 



I have not carried out the examination in the antennje 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 

 tmtenna, 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 cutieular 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 xTrtv 

 inch diameter, but on a side view they are seen to be depressions of the surface, the internal 

 wall being pei'forated, with a very thin membrane closing in the perforation, which is 



