50 ©. R. Osten Sacken: on Mr. Portchinski's publications 
The larya of Lucilia caesar (the green bottle-fly) passes through 
the same stages of development, and its larvae, except in size, are 
undistinguishable from those of ©. erythrocephala. Still it would 
be premature to conclude from the resemblance of the larvae to the 
close relationship of the mature flies, and to infer that flies of a more 
distant systematic position would necessarily have very different 
larvae. Oynomyia mortuorum is structurally very different from 
Calliphora, so different in fact that it is usually referred not to the 
group of Muscinae, but to the Sarcophaginae. Nevertheless, 
instead of being viviparous, like the Sarcophagae, Oynomyia mor- 
tuorum is oviparous, and its larvae are, in all their structural de- 
tails, so much like those of the Calliphora (blue-bottle fly) that it 
is impossible to discover any distinctive character. 
The larvae of these three flies are true carrion-eaters; they 
are exactly alike and have the same mode of development. 
In order ‚to test the food-habits of these larvae, they were bred 
from the egg. The flies, being confined within a closed receptacle 
containing a small piece of meat, soon begin to lay eggs in quanti- 
ties1); — it is an easy matter afterwards to transfer them for hat- 
ching in different other substances, according to the nature of the 
experiment to be tried on them. Eggs of the blue-bottle fly and of 
Cynomyia were placed at the same time on meat, on cattle-dung 
and on decaying mushrooms, and it soon became evident that they 
could thrive on meat only; in the two other environments they grew 
very slowly and finally perished. The same result was obtained 
with Zueilia caesar, except that the larvae put in cattle-dung did 
not perish, but grew slowly. 
We have said that the larvae of these three flies are almost 
undistinguishable from each other, and pass through the same three 
larval stages. Still, there is one important difference between their 
life-histories: the blue-bottle and the green-bottle lay from 300 to 
600 eggs, while Cynomyia does not lay more! than 150. All the. 
specimens of the fly which were dissected did not contain more than 
150 eggs, generally less. All other conditions being equal this diffe- 
rence in numbers is a disadvantage for the fly, and hence among 
the three carrion-flies Oynomyia is the rarest. In the spring of 
certain years Cynomyia is unusually abundant, and then the blue- 
bottle is rare and appears in the beginning of June only. Carrion, 
1) Some species of flies do not like to lay eggs in confinement, 
and for this reason the observation of their habits is much more 
difheult. 
