AERIAL AND TERRESTRIAL DIPTERA 
201 
principal organ of orientation in this superfamily. As if in com¬ 
pensation for their small heads and eyes, the Nemocera vera show a 
large development of the antennae. It is in them, and not in the 
conformation of the eyes, that the cephalic secondary sexual char¬ 
acter finds its expression (130. 1892, p. 434). We have seen that, 
among the Diptera Brachycera , the holoptic head of the male is 
generally an index of the power of regulating flight. Among the 
Nemocera vera , in the absence of holoptic heads, it is the long anten¬ 
nae and the long legs that regulate flight. The antennae, in such 
cases, besides their function as organs of orientation, make them¬ 
selves useful as organs of action (for this distinction, compare 
above, p. 193). All the dancing and swarming Nemocera vera 
have either long or otherwise much specialized antennae, and, at 
the same time, long legs ( Culicidae , Chironomidae , Tipulidae ). 
Although Culicidae are prevailingly aerial, their relatives, the 
Psychodidae , with their shorter and stouter body and comparatively 
short legs and wings, have the habits of pedestrian Diptera. And, 
indeed, I have observed small Psycliodae running round in a circle 
(on a glass-pane) with a remarkable rapidity. 
Among the Chironomidae , which are generally aerial, some Cera- 
topogons possess decidedly terrestrial characters in their compara¬ 
tively short and strong legs, their femora armed with spines or 
bristles, and their tibiae and tarsi displaying a variety of adaptive 
structures. 
Among the Nemocera vera , the majority of which, as we have 
seen, are aerial, the Mycetophilidae are remarkable for their terres¬ 
trial and pedestrian habits. Rob.-Desvoidy, in his picturesque 
style, described them well as “ the timid species living under the pro¬ 
tection of rotten mushrooms” (Rob.-Desvoidy, “ Myodaires,” 1830, 
Preface). Their antennae have no verticils, and are of a simple 
structure in comparison with that of the antennae of other Nemo¬ 
cera vera; their legs are stouter and stronger. Nevertheless, 
among these terrestrial Mycetophilidae there are genera which pre¬ 
serve the generally aerial character of the superfamily Nemocera 
vera ; Macrocera and Bolitophila , with their long legs, their long, 
filiform antennae, and their slender, elongate bodies, have the 
appearance of Limnobiae and share their aerial habits. 
