AERIAL AND TERRESTRIAL DIPTERA 
197 
tic heads in the male sex and the specialization of the legs. I 
begin with the family Stratiomyiidae. 
In the section Beridina we have the European Actina and the 
Australian Exaireta, both with dichoptic eyes in the male sex; 
while the closely allied genera ( Beris , Allognosta , etc.) have holop- 
tic males. In Bxaireta the pedestrian tendency is distinctly indi¬ 
cated by the development of the legs. 
In the section Sargina , the genus Histiodroma , described by 
Schiner (“ Novara,” p. 68, tab. II, f. 8), has a broad front in both 
sexes. He places it in a separate section, Raphiocerina. Not hav¬ 
ing had an opportunity to examine specimens, I cannot judge 
whether the dichoptic male of Histiodroma shows, besides this, any 
other pedestrian tendency. 
In the section Hermetina , the genus Hermetia shows a broad 
front in both sexes, while its Australian close relative Massicyta 
Walk. ( Lagenosoma Brauer, “ Notacantha,” p. 81), according to 
Brauer, Walker had only females, has an holoptic male, which 
proves again that holopticism in this case, as in many others, is 
not a deep-seated character. 
In the section Stratiomyina ( Odontomyina Loew) I am not aware 
of any exception to the rule of male holopticism. In some genera 
only ( Buparhyphus , Lasiopa') the eyes of the male are subcontiguous. 
Among the PacJiygastrina subcontiguous eyes likewise occur; 
but I find only Chauna Loew, from Cuba, which is described as 
having, in both sexes, “ a broad, smooth front.” 
In the family Tabanidae I have not discovered any exception to 
the rule of holopticism; it may occur nevertheless, as many genera 
and species are described in the female sex only; and as, in some 
generic descriptions, the holopticism of the male is not distinctly 
mentioned, and probably taken for self-understood. 
It is in the predaceous family Leptidae that a number of genera 
assume, in their general appearance, as well as in the details of 
their organization (in a dichoptic head in both sexes; in the struc¬ 
ture of eyes and antennae; in tlieir slender body and legs), a 
striking resemblance to the Asilidae , mimicking them in such a 
degree that several of them were actually placed in that family by 
otherwise experienced entomologists. The Leptid Pheneus was 
