1948] 
Bailey — Tab an us atratus 
137 
on the saltmarsh. It appears that these names designate 
the extreme forms in a population showing marked vari- 
ability. Whether the basis of this variability is genetic, 
the result of physiological responses to environmental 
factors or, perhaps, both deserves investigation. Present 
evidence at least suggests that the fulvopilosus condition 
may be sex linked inheritance. Since there are females 
with both varietal characters and with no other recognized 
differences, the validity of distinct names seems question- 
able. On the other hand, if the form of the atratus egg 
mass has the specific significance indicated by Schwardt 
(1936), the status of nantuckensis needs clarification from 
this angle as well. 
A few observations on the larvae and pupae demand 
notice. The former are most commonly found under mats 
and piles of straw and other plant debris which becomes 
stranded in soggy spots subject to frequent tidal flooding 
or sufficiently depressed to hold rain water. Where such 
trash lies on soft mud in very shallow water they are 
especially common. If uncovered they retreat by bur- 
rowing rather rapidly into the surface muck. Now and 
then one may he found in the thick algal mats on the sur- 
faces of deeper pools. These saltmarsh larvae closely re- 
semble typical atratus larvae as described by Walsh 
(1863), Riley (1870), Stone (1930), et al. but should he 
examined critically for possible differences. It would 
also be interesting to rear some under conditions com- 
parable to (a) salt and (b) fresh marsh habitats to deter- 
mine what influence, if any, the environment has in the 
production of the variation characteristic of the adults. 
Pupal cases are often numerous in the drift left at the 
edge of the marsh by exceptionally high tides. This 
leads one to wonder at the relative scarcity of the flies 
themselves. The cases may also be found protruding 
from heaps of straw along the ditch banks. Yet only 
rarely are living pupa? encountered. One was located on 
the Parker River saltmarsh just east of Route I on July 
17, 1947, and a male emerged on July 21st. This speci- 
men was killed while still somewhat teneral and was 
reared indoors. The coloration of his wings is only 
slightly less uniform than in typical atratus. 
