148 DR. J. BRAXTON HICKS ON UNDESCRIBED SENSORY ORGANS IN INSECTS. 



hairs of the general integiiment is a matter of much diffiralty, compared with that of the 

 members where the nerve can be easily traced throughout its course. 



I now wish to call attention to the anatomy of the " barrel-shaped" organs (as they 

 are called) on the proboscis of the Lepidoptera. They are found in ahnost all genera 

 of English Butterflies and Moths. The genera Fontia, Pieris, Gonopteryx, and the 

 SpldngidcB, are free from them, as is also the rudimentary proboscis xa.t\\e Bomhycidoi and 

 Tiger Moths. Perhaps they are shown best in Argynnis Paphia and Vanessa Atalanta 

 among the Dimma, whilst among the Noctua Mormo and Trtjphcena possess them exceed- 

 ingly well marked. In those species where they are not present, dwarfed hairs are found, 

 in rows on the proboscis ; but whether they are in the same position as the barrel organs 

 woidd haA^e been in, I cannot decide. 



The form of the barrel organs is very variable ; but they may be divided, so far as I 

 have had the opportunity of examining in British Lepidoptera, into two divisions — the 

 simple and the winged ; the latter I have found only in the Moths, whilst the simple are 

 confined to the Diurna. The simple form is shown at PI. XIX. fig. V, 1, which represents 

 that of the Argynnis Paphia. They are flattened in one direction. The winged are 

 shown at PI. XIX. fig. V, 5, being those of Ilormo Maura (Moth). The section at 6 

 Indicates the position of the wings on the body of the organ. 



The essential part of the barrel organs is a tube more or less dilated towards the 

 middle, contracting again towards the apex, and terixdnating in a nipple-like point, —the 

 membrane of this papilla and for some distance around its base being very thin and deli- 

 cate ; and, at the point where this thinning commences, a very delicate tissue stretches 

 across the interior of the organ. A nerve can be traced up to this membrane for that 

 certainty, as is shown at figs. V, 1 & 4, in Argynnis Paphia. I am tolerably certain that 

 a delicate filament passes to the apex of the papilla (fig. V, 2) ; or if that is not the true 

 interpretation of the appearance, then I think it must be produced by a very delicate 

 tube passing from the apex of the papilla into the interior of the barrel organ. This point 

 is difficult to settle on account of the delicacy of the parts to be investigated. In the 

 Vanessce and many other Diurna, there is a ring of eight spines around the papilla, which 

 spring from the part where the thinning commences ; and in the Moths there are seven or 

 eight rings springing from the whole length of the barrel organs, ending at the point just 

 mentioned. The upper points of the rings and of the spines, as in Vanessa, do not, I 

 believe, ever extend to the length of the papilla. That these organs, where they exist, are 

 used for some refined sense, one can hardly doubt, but of what nature it is very, difficult 

 to decide. Whether it is to the sense of touch that they confine that highly- developed 

 variety of it which wc call taste, we are not at present competent to judge. The anato- 

 mical resemblance of these organs to that on the palpus of Foi^ficida will be apparent 

 to all. 



In considering what functions we are to assign to the various structures I have just 

 described, we have to bear in mind that a too strong dependence on analogy of position 

 of the different parts of Insects, and of the Invertebrata in general, to those of the higher 

 animals will tend to mislead us ; for as the ganglionic nervous system is itself diffused far 

 beyond the state it is in the Vertebrata, so we may possibly find that the special sensations 



