168 
Psyche 
[June-August 
Tf we accept the foregoing suggestions as being more or less 
correct, several families — the Dolichopodidae, Therevidse, Asilidse, 
Empididae, and a few others, are left without indications of 
their origin, and it must be admitted that it is difficult to as- 
sociate these families with any of those usually placed lower in 
the scale. However, there can be little doubt that these and 
allied families form a natural group and it is not difficult to 
trace true or fancied relationships from one family to the other. 
It may be necessary to eliminate the Tabanidse from the line of 
direct descent and to consider for the present that they form a 
natural branch, therefore concluding that the Asilid group, 
through the Empididse, are related to such forms as the Bibionidse 
or even the Blepharoceridse. 
Malloch has recently pointed out that the Pyrgotinac are 
evidently related to the Conopidse, a view in which I concur. 
This indicates rather forcibly the relationship of the Pipunculidse 
and Acalyptratse. 
If we consider the matter from the viewpoint of squama^ 
development, we find that the squamae are large in the Tabanidae) 
Stratiomyidae, Syrphidae, Muscoids and Tachinidae, at least in 
so far as many members of these families are concerned. The 
exact value of this structure from the taxonomic point of view 
has not yet been determined. I am inclined to believe that it is 
a development more or less confined to robust species which 
are, or have been in the past, hoverers. Such a development 
seems to have been induced in flies which bred in liquid media, 
as the large squamae have disappeared to a very large extent in 
those Syrphidae which do not pass their early stages in such 
surroundings. If the squamae have developed due to this habit, 
they must be looked upon merely as indicating habit and cannot 
be considered too seriously by the taxonomist. 
Further, in connection with the squamae, it should be 
pointed out that a character which is almost universal with the 
Stratiomyidae occurs in the families enumerated in the preceding 
paragraph, but is not general. This is the presence of fine hairs 
or sparse pile on the upper surface of the lower squama, a charac- 
ter which is very evidently derived from the pubescence usually 
