138 Mittheil. d. Münchener Ent. Ver. 1881. 
or less striking manner from ordinary hairs. Thus im 7oxo- 
phora there is a number of conspicuous macrochaetae on the 
thorax; but as their bases are hidden by other, shorter hairs, 
their homologies can only be guessed at; on the head, there 
is an ocellar pair, but no other macrochaetae. Mulio obscurus 
has many macrochaetae about the thorax, the nomenclature 
of which is as uncertain as that of the macrochaetae of Toxo- 
phora ; the abdomen of Mulio also, shows conspicuous rows of 
large bristles. The north-american Systropus,, although so 
little hairy, that the macrochaetae would be easily perceptible, 
has none whatever. The same may be said of Phthiria. In 
the genera of Anthracina and Bombylina, which form the bulk 
of the family, the dense hairmess or fur prevents to discern 
any macrochaetae, Still, traces of them may be occasionally 
seen. For instance, among the yellowish fur of some Bomby- 
li, a pair of black hairs are often visible above the root of 
the wing, which may represent supra-alar bristles; in Anthrax 
flava and congeners, a tuft of macrochaetae exist on the post- 
alar callus. 
Therevidae. With the 'species of Thereva, which are covered 
with a dense fur, we experience the same diffieulty as with the 
Bombylidae, but that diffieulty vanishes with the glabrous or 
subglabrous species, and here we at once observe much more 
marked homologies with the normal chaetotaxy of the other 
families, There are none of the normal cephalic pairy bristles; 
even the ocellar pair, elsewhere so persistent, is wanting. No 
humeral bristles; a row of three or four bristles, which must 
be considered as posthumeral, as they are inserted on the 
triangular praesutural depression (which is distinet)y visible 
here, although it cannot exactly be called a depression). Two 
anterior supra-alar bristles (on the edge of the anterior supra- 
alar cavity), and one posterior (on the post-alar callus). Two 
pairs (sometimes only one?) of praescutellar bristles, one ex- 
actly in front of the other. Four seutellar bristles. 
