1148 
It might reasonably be supposed, that the chance of encountering 
a more primitive design would be greater in forms provided with 
a more original nervural system, which in Diptera-is equivalent to 
a more complete one. However Il hope to be able to argue that 
this is not necessarily the case. 
Notwithstanding this I think it is preferable to start from forms 
with a less modified nervural system, e.g. the genus Haematopota, 
containing a number of species, whose wings show a rich but at 
the same time regular ornamentation. 
Comparing the four species: italica, tubereulata, pluvialis and 
maculata, it is beyond doubt, that in alt of these the colour-markings 
are arranged according to the same groundplan, which in italica, 
pluvialis and tubereulata is more fully and regularly developed than 
Fig. 1. Haematopota pluvialis. 
Fig. 2. Haematopota maculata (De Meijere). 
in maculata, the latter showing the proximal half of its wings 
almost destitute of markings, except a few irregular patches, while 
the distal part contains two transverse rows of dark markings, those 
of the outer row being smaller and more isolated, those of the 
inner (submarginal) broader and connected to a continuous band. 
In both parts however the extension of the markings is limited by 
