Östen-Sacken: An essay of comparative Chaetotaxy. 123 
flieting terminologies of previous writers, and for this reason, it de- 
serves the highest consideration. In the nomenclature of bristles, I 
have taken into account the terms introduced by earlier writers, as 
far as consisteney permitted it. 
Not sufficient attention has been paid to the functions of the 
macrochaetae in Diptera, and to the remarkable eircumstance, that 
while they occur, with great regnlarity, through a long series of fa- 
milies, they are wanting in others. 
Among the Orthorhapha, the diptera eremochaeta (bristleless) form 
the rule, the chaetophora the exception; but this exception comprises 
the large and important families of Asilidae and Dolichopodidae. (The 
bristles on the legs of the Mycetophilidae and Culicidae cannot are 
not properly macrochaetae.) 
Among the Cyelorhapha , the diptera chaetophora are the rule, 
the eremochaeta form the exception, but a very important one, the large 
family of Syrphidae. 
Maequart thinks, and he may be right, that the macrochaetae 
serve as a protection to the parts of the body upon which they are 
inserted ; that they act as buffers in cases of sudden contact. In 
the Introduction to his: Nowvelles Observations sur les Tachinaires 
(Anm. Soc. Entom. Fr. 1845, p. 239—- 240.) he says: „En exami- 
nant la situation et la direction de ces soies, qui sont d’ailleurs les 
memes dans la plupart des Museides, il est impossible d’en mecon- 
naitre la destination. Elles protegent toutes les parties superieures 
de la töte contre les chocs, et l’on ne peut guere douter que ces 
moyens de preservation n’aient ete accordes A cette famille immense, 
ä Texelusion de la generalite des autres dipteres, pour compenser la 
faiblesse des teguments. Les quatre soies oceipitales, en se dirigeant 
en arriere, defendent le cou; les deux stemmatiques, tournees en avant, 
previennent les dangers auxquelles les ocelles sont exposes,, surtout 
pendant le vol; les laterales du rang interieur, dirigees en dedans, 
forment une voute pour abriter le cräne qui recouvre le cerveau; 
enfin, celles du rang inferieur dans les femelles, tournees en avant, 
defendent les cötes du front, @largis dans ce sexe,‘“ Macquart might 
have continued in the same strain about the bristles of the thorax: 
the supra-alar bristles proteet the root of the wings from above; the 
mesopleural perform the same office in front; the metapleural fan of 
