96 
Psyche 
[June- August 
table matter. Their habitat is not limited to Europe. In Amer- 
ica Felt^ found Miastor larvae in 1910 under the partially decayed 
inner bark of chestnut rails. 
In such environments Miastor larvae usually occur in charac- 
teristic, compact, white colonial masses, a colony often con- 
taining a hundred or more individuals in close contact with each 
other. Among Miastor larvae occurring in mushrooms I have 
not observed colonial ^arrangement. Here yellow or yellowish 
white larvae are found singly although a single plant may con- 
tain many larvae directly beneath the superficial cell-layers of 
the stalk or between the gills of the umbrella. 
The Life-Cycle of Miastor. 
Paedogenetic reproduction maintains in this genus during 
the autumn, winter, and spring, until the early summer, at 
which time pupae occur, producing, after metamorphosis, male 
and female imagines. (The occurrence of pupae, however, is 
not limited to the early summer. I have found them in nature 
in October, and in the same material pupae continued to arise 
in the laboratory during the early winter. Though these were 
kept in conditions as natural as possible, at room-temperature, 
none of the pupae has as yet given adults, though the usual 
period required for this metamorphosis in Miastor is about five 
days. Some of the pupae have been destroyed by mould. It 
would seem that others, apparently in good condition, are in 
diapose.) The copulation of the adult flies results in the fer- 
tilization of the eggs which develop outside the mother into 
typical paedogenetic larvae, and the cycle is complete. 
Paedogenesis in Miastor is realized as follows: The ovaries 
of a typical paedogenetic larva produce eggs varying in number 
in different individuals, types and species. The development of 
larvae from the eggs occurs within the body-cavity of the mother. 
The embryos continue to develop at the expense of the fat- 
bodies, muscles and surrounding tissues of the mother larva until 
ipelt, E. P. Miastor americana, an account of Pedogenesis. Bull. New York State 
, 1911 vol. 147, pp. 82ff. 
