on the larvae of Muscidae. 25 
instance Mesembrina meridiana and Spilogaster divisa are vivi- 
parous, while Mesembrina mystacea and Spilogaster angelicae lay 
only a small number (24 or less) of large eggs, the larvae omitting 
the second stage of development). 
The biologies hitherto discussed were those of flies belonging 
to the northern regions of Russia, prineipally the environs of St. Pe- 
tersburgh. But Mr. Portschinski extended his observations to the 
south of Russia also, and brought home very remarkable results. — 
One of the most common coprophagous flies in the south of Russia 
is Dasyphora pratorum; we have already stated above that its 
larva shows but trifling differences from that of Musca corvina; 
the imago’s resemble each other likewise, although less than the larvae. 
There must necessarily exist a severe competition between the two 
so. closely related flies, and this competition must have had its in- 
fluence on the biology of Musca corvina in those southern regions. 
Now the mode of larval development of Dasyphora pratorum is 
very peculiar. A comparatively large, usually oblong egg detaches 
itself from one of the ovardes and remains in a matrix-like receptacle; 
there the larva is hatched and begins to grow; the structure . of its 
posterior stigmata indicates the first stage; upon further growth, the 
second stage is reached, provided with stigmata with double fissures; 
and finally the third (with the three fissures). It is in the third 
stages that the larva is laid by the fly, and deposited in the dung of 
horned cattle; it very soon reaches its full growth and goes under- 
ground for its further development. It is very probable that, one 
larva being laid, a new one is soon developed within the body of 
its mother; the ovaries show its beginnings. 
The biology of this fly is not unlike that of Hylemyia strigosa, 
as, in both cases, a single large larva is laid; but with this great 
ı) This latter fact is not explicitly stated, but must be inferred 
from the context, especially in connection with the passage beginning 
at the bottom of p, 14: ‚„‚Thus the larvae of coprophagous flies, Musc« 
corvina, meditabunda etc. that lay a small number of very large 
eggs, do not pass through the second stage.‘ On p. 13 the copropha- 
gous flies laying a small number of large eggs are enumerated as fol- 
lows: M. corvina, meditabunda, Mesembrina mystacea, Spilogaster 
angelicae, Pyrellia serena and Graphomyia maculata. Therefore 
we have a right to infer that the author’s meaning is that all these larvae 
omit the second stage of development. But it is not quite clear at the 
same time whether this generalization is a mere inference, or is based 
on actual observations; the only observation expressly mentioned by 
the author is that on Musca meditabunda, which he saw pass directly 
from the first to the third stage. 
