168 ©. R. Osten Sacken: 
In the Dolichopodidae and Asilidae we have instances of fami- 
lies of the same kind, and the words of Mr. Loew about the latter 
„that not a single dipteron has yet been found, the position of which 
as belonging or not belonging to this family is questionable” — these 
words may, with almost equal propriety, be applied to the Tipu- 
lidaeı). 
The presence of a V-chaped transverse suture across the meso- 
notum would alone be sufficient to distinguish the Tipulidae from 
the neighbouring families. The completeness of the venation and 
the structure of the ovipositor of the female are of equally general 
application. Through the whole family, and all the modifications of 
the other organs notwithstanding, the venation is arranged according 
to the same plan, the characteristic features of which are, the great 
length of the two basal cells, the development of the auxiliary vein, 
and the presence, in the majority of cases, of a discal cell. The 
veins, in their last subdivisions along the margin of the wing, are 
from ten to twelve in number (if Cladolipes and Toxorrhina have 
only nine veins, the obliteration of a vein in both cases is evident). 
The Culicidae and Psychodidae come next to the Tipulidae 
with regard to the completeness of the venation; but they have no 
discal cell; among all the other Diptera nemocera this cell 
oceurs only in Ahyphus. 
The size and structure of the ovipositor, with its two pairs of 
horny, pointed valves, is common with very rare exceptions to all 
the Tipulidae (the ovipositor of the other Diptera nemocera 
generally consists of two hardly projecting inconspicuous valvules). 
The only genera exceptional in this respect are Oryptolabis and 
some of the Ptychopterina (Bittacomorpha, Tanyderus, Idio- 
plasta); their ovipositors do not show any horny appendages, but a 
pair of coriaceous valyules instead. 
The three leading characters of the Tipulidae — thoraeie 
suture, venation and the structure of the ovipositor —, sufficiently 
isolate this family among the other Diptera nemocera; but we 
render the contrast still more striking, if we direct our attention to 
1) At the time when Loew wrote these words (1847), Apiocera 
Westw. 1835, was very little known and Jtaphiomidas O0. S. 1877 
was not discovered. Later (in litteris) he acknowledged their rela- 
tionship, but took them both for Midaidae. At that time tlıe Chaeto- 
taxy was not worked out and Loew does not seem to have noticed 
that Midaidae never have any macrochaetae. Had he been alive now 
he would not have hesitated to recognize both genera for Asilidae. 
