154 
NOTES ON CHAETOTAXY 
At present, in questions of classification, we use cliaetotactic 
characters as sure, indispensable, and easily applicable indexes 
of affinities. But, before 1880, the want of appreciation of these 
characters brought about hypothetic relationships established 
merely upon superficial resemblances, or upon characters of but 
secondary importance. The result was that groupings and arrange¬ 
ments were adopted which now appear to us simply preposterous. 
Beginning with myself, I must acknowledge that for more than 
twenty-five years, I had been studying Diptera without feeling any 
necessity for an improvement in the method of describing their 
bristles and hairs. As late as 1877 I described Rhaphiomydas as 
a Mydaid, a notion which, three years later, appeared to me 
absurd. 
The explanation of this apparent obtuseness on my part, how¬ 
ever, is rather easy. During my residence in the United States, 
although I was collecting all Diptera, I studied and worked up 
monographically the Tipulidae , Cecidomyiidae , and Tabanidae , 
families which are not provided with macrochaetae. It was only 
after my return to Europe that I undertook the study of Asiatic, 
African, and Australian Diptera, and thus came into contact with 
forms of all families. In 1880, while at work on my “ Enumeration 
of the Diptera of the Malay Archipelago,” which appeared in 
February, 1881, although 1 had for the first time to describe a con¬ 
siderable number of Diptera Cyelorrhaplia abounding in macro¬ 
chaetae, I still followed the old routine. Thus, in describing the 
Ortalidgenus Anguitula ( loc. cit ., p. 482, line 6 from bottom) I said: 
“No bristles at all on the head; the usual erect bristles on the 
vertex are replaced by a few hairs, visible only under a strong 
lens,” etc. But when, later, I was preparing my “Supplement of 
the Enumeration,” and had to describe a very bristly fly, a Dexid 
( Urodexia , gen. n.), it occurred to me that the distribution of such 
conspicuous bristles must be subject to some rule. I took my 
time, worked out ray “ System of Chaetotaxy,” and published my 
first paper upon it in 1881 ; my “ Supplement of the Enumeration ” 
appeared in February, 1882. The thoracic bristles of Urodexia are 
described in it chaetotactically as follows : “ Four dorso-central 
rows; the outer ones of five bristles each; two intrahumeral bris- 
