NOTES ON CHAETOTAXY 
157 
Rondani ( Nuov. Ann. Sci. Nat., Bologna, 1845), when introdu¬ 
cing the name macrochaetae, did not exactly define the concept, but 
explained the name as follows: “ A word which may be translated 
by another one: crassisetae, and thus the ordinary term setae will 
remain for bristles distinctly more slender (‘ piu esili ’), and the 
temtpili for those which are the most delicate (‘ sottilissime ’) 
In my “ Essay” ( Trans. Ent. Soc ., London, 1884, p. 501, at top), 
I went a step farther in describing macrochaetae “ as organs of 
orientation , not unlike the whiskers of a cat.” Such sensitive 
organs, it may be readily assumed, must be connected with the 
nervous system, the nerves penetrating to them through the chiti- 
nous integument of the fly, and this penetration is indicated by 
the scar which macrochaetae leave behind them when rubbed off. 
Anatomists may, by and by, go beyond these hints, and add many 
new facts to our knowledge about the role of macrochaetae as 
organs of orientation. 
A still unrealized desideratum is a Chaetotaxy of the legs of Diptera, which 
would enable describers to define their position with exactness, as well as brevity. 
The first attempt of this kind was made by J. Mik. In his “ Dipterologisehe 
Untersuchungen,” Wien, 1878, p. 3, footnote, he says: “On the legs I distinguish 
a front- and a hind-side ; an upper- and an under-side. When we imagine the leg 
stretched out horizontally and perpendicularly to the longitudinal axis of the 
body, the front-side is that which is turned towards the head, and the hind-side 
that turned towards the end of the body ; the upper- and under-side, in such a 
case, are self-understood.” 
I accept this proposal as expedient, but I would improve it by the addition of 
appropriate terms for intermediate positions. Assuming any femur or a tibia to 
have the shape of a more or less irregular cylinder, we may define the position of 
a bristle, or of a row of them, as being inserted on its upper (superior)-, or under 
(inferior)- side, or on its front (anterior)- or hind (posterior)- side. A bristle, or 
a row of them, may be situated on the line (edge) between the superior and ante¬ 
rior side; or between the anterior and posterior side, etc. In such a case I would 
describe them as inserted on the supra-anterior, the supra-posterior, the ante- 
inferior and post-inferior side. 
For brevity’s sake a mode of notation might be adopted, analogous to that used 
for the points of the compass: S (supra), I (infra), A (ante), P (post); and in 
combination: S. A. (supra-anterior), S. P. (supra-posterior), A. I. (ante- inferior), 
and P. I (post-inferior). 
For still closer definitions of position, the combinations S.S.P., or S.P.P. etc., 
might be used, just as for the points of the compass. 
It is evident that the minuteness of such characters, their multiplicity, their 
unsteadiness, as well as the difficulty, in some cases, of obtaining specimens in a 
