340 THE AMERICAN NATURALIST. [VoL. XXXV. 
two described below, had best be considered as the subfamily | 
Stethopathine of the Phoride. 
It does not seem probable that the forms have had a common 
origin however ; even their distribution would preclude this 
in the case of such a recent group. On the other hand, there 
seem to be several independent lines of descent which we can 
to some extent suggest. In Psyllomyia the degeneration con- 
sists in the reduction of the eyes, absence of ocelli, and reduc- 
tion of wings. In Commoptera the eyes are larger, the ocelli 
present ; but the abdomen is extremely degenerate in structure, 
being almost wholly membranous. Ecitomyia could be more 
easily derived from forms like Commoptera, as it has very 
rudimentary wings, no halteres, smaller eyes, smaller thorax 
(without scutellum), and about equally degenerate abdomen. 
The degeneration has gone furthest in the genera from the 
Bismarck Archipelago and west Africa. Here the thorax is 
exceedingly small, the wings and halteres completely lost, the 
eyes very small, and the abdominal segments more or less mem- 
branous. Of these Stethopathus alone has retained distinct ocelli. 
Wasmann’s Termitoxenia has the immensely swollen abdomen 
so characteristic of all termitophiles, and a greatly modified head. 
It does not approach closely to any of the other genera. 
The following table, showing the order of degeneracy with 
regard to different structures in the genera of the Stetho- 
pathinze as compared with Phora, will serve to emphasize the 
great disparity between the genera. Phora is placed at the top 
in each case and the most degenerate genus at the bottom.! 
Wings. | 
EYES AND OCELLI. ABDOMEN. | THORAX. 
no Te aa 
Phora : Phora Phora Phora 
Psyllomyia Commoptera Psyllomyia Commoptera 
Commoptera Termitoxenia Chonocephalus | Psyllomyia 
omyi Stethopathus Stethopathus Termitoxenia 
Termitoxen Psyllomyia Ecitomyia Ecitomyi 
Stethopathus Wandolleckia Commoptera tethopathus 
Wandolleck Ecitomyia Wandolleckia Wandolleckia 
Chonocephalus | Chonocephalus | Termitoxenia Chonocephalus 
1 Where ocelli or wings are absent I have judged by the size of the eyes and 
h 
the thorax. 
