64 
Psyche 
[June-September 
A great deal has been written about the group of species 
related to the form named above. Out of this there has de- 
veloped a welter of species : brevicauda, quadrioculata, 
manolachei, nana, microchaeta, penicula and multiseta. 
Further than this when we considered the excellent work 
of Agrell upon variation in eye number we can add to this 
group at least the one-eyed forms such as regularis, dip - 
lopthalmia, agrelli, ksenemani, pseudodiplopthalma, similis , 
and monopthalma. Most of these so-called species differ by 
very few characteristics, indeed often only by one. These 
are commonly chaetotaxy differences and there is not the 
slightest bit of evidence to deny the possibility that they 
represent single gene variations. Thus the differences seen 
could well represent in some cases balanced polymorphism, 
and in others ecotypical selection for a given gene. Further 
than this most of the species here mentioned have been 
studied at one time from a few relativley homogenous 
habitats and there is thus little opportunity to study the 
variation through a wide range of conditions- I wish to 
suggest that there is at present insufficient evidence to sort 
out accurately from the forms mentioned above more than 
a few forms and be able to say with any degree of assurance 
that they actually represent different species. The speci- 
mens studied below appear to be classifiable as two species, 
F. quadrioculata and F. penicula. If we accept this thesis, 
then it is possible to sort out the specimens at hand quite 
readily on the basis of the ventral manubrial chaetotaxy. If 
we sort them out thus, it appears that with few exceptions 
a given collection or sample is of one form or the other. 
If an attempt is made to sort out the populations on any 
other basis, this is not so and most samples are mixed. 
Further, in a statistical sense it is possible to sort out these 
two species upon about five additional characteristics ; how- 
ever, none of these shows very good correlation with the 
manubrial chaetotaxy. For purposes of illustrating the dis- 
tribution of some of these characteristics through the pop- 
ulation, a large number of specimens from twelve localities 
was sorted out to quadrioculata or penicula on a basis of 
the ventral manubrial setae. Fifteen specimens were chosen 
from each species and checked for a number of character- 
istics. The results are indicated below. 
