1149 
by obliteration of the separating vein, remains unexplained on 
DE Mruere’s hypothesis. 
Yet it must be conceded, that it would not be reasonable to assume 
a coalescence of cells in every case where nervures are accompanied 
at both sides by rows of light or dark spots, however far the infe- 
rence, founded on the comparison of Sciomyza to Traginops, seems 
justified to me, that a dark median bar can be replaced by a light 
one, and in this way all traces of the original duplicity of the cell 
can “be obliterated. In the case of e.g. Poecilostola such an assump- 
tion is out of the question, except for the cells Cu,—An, and An,— 
An,. The same feature is seen in Hepialids among Lepidoptera, 
which also often show the hourglass- or dumbbell-shaped spots 
separated into two halves, adjoining opposite nervures, and so forming 
paramedian rows of independent. spots. Black median bars may there- 
fore also be simple remnants of the general dark ground colour. 
Fig. 7. Cleitamia astrolabei 2 (Boisd). 
Fig. 8. Trypeta cribrata 2 (v. d. Wulp). 
