252 DIPTERA 
course variable, third vein forked, the upper branch rather erect, stigma present or absent, pedicel of 
the second and third veins very short; otherwise the neuration varies greatly as outlined below. 
Ethology : These odd little flies with their semi-translucent legs and bodies, are the most delicate 
of the Empididz. They occur, never in large numbers, in shady sheltered spots in the woods, usually 
near water, running over herbage and low shrubbery. Sometimes the species occur in houses, where, 
as Mrs. Slosson has said: «as they run upon a window-pane with the light behind them they seem mere 
shadows, little ghosts, frail, elf-like things». Some species are nocturnal, and are attracted to lights. - 
Brocher, who has recently studied the life-history of C. £recatoria, found the larva in the mud of 
streams. The larva is slender, but tapers in front, its posterior end is furnished with five or six diverging 
hairs, and ventrally it has seven pairs of retractile propodia. The pupa has paired tracheal filaments, 
each two-thirds as long as the body, attached at the spiracles, and including one prothoracic and seven 
abdominal pairs; it has no dorsal spines but merely girdles of setulze on the abdomen. — The pupal period - 
lasted thirteen days. 
Taxonomy : The old genus Hemerodromia has had a host of synonyms. While many of the 
names were bestowed as subgenera on certain permutations of three neurational characters, — namely, 
the presence or absence of the discal cell, the presence or absence of the anal cell and the shape of the 
second posterior cell, whether sessile or petiolate, — others are pure homonyms. The usual custom 
has been to consider these groups as subgenera, since they were based on but slight variations of the 
venation. These so-called subgenera have been characterized as follows : $ 
Discal cell Anal cell Second posterior cell 
Hemerodromia, Meigen, s. str. imperfect absent ; petiolate 
Metachela, Coquillett imperfect present petiolate | 
Neoplasta, Coquillett : imperfect present sessile 
Chelifera, Macquart present present petiolate 
Cladodromia, Bezzi present present sessile 
If such variations in wing venation were not correlated with other characters the groups would 
be artificial and could have at most but subgeneric rank, for the second posterior cell, e. g. in 
Cladodromia, varies from sessile to V-shaped, and even to Y-shaped with a short petiole, and MetacAela 
as defined included two species, one with the discal cell fused with the second basal and the other with 
it fused with the third posterior cell. However, a closer inspection shows that the trivial differences in 
neuration are associated with more fundamental characters in the structure of the wing and correlated 
at the same time with differences in the form of the body. Accordingly, the old genus Hemerodromia 
has been segregated into two distinct groups, Hemerodromia, s. str. (i. e. Microdromia) and Chelifera. 
The remaining groups are less important subdivisions of the latter genus, although Chelifera, s. str., 
with its thorax tapering anteriorly, may ultimately be removed from the broad-shouldered others, and 
Neoplasta with its narrow face and slender front legs may likewise be segregated from the rest. In 
addition, another genus has been erected for two Central American species whose neuration superficially 
resembles that of N'eoplasta. 
Concerning which of the restricted groups should bear the name Hemerodromia there has been 
much discussion. As this can be settled only by ascertaining the type species, various writers have 
argued as variouely for this or that genotype. The following statement shows the nomenclatural status 
of Hemerodromia and its allies. 
Hemerodromia, Meigen. Meigen originally described nine species under this name; the ffth, 
mantisba, Panzer, was selected as the type by Westwood, in 1840. However, in 1823 Macquart had 
