FEBRUARY 16, 1912] 
chitinous spines, best developed on the ante- 
rior body segments. These larvee are 144, to % 
of an inch long and may occur in small 
clusters in the bark or form dense masses cov- 
ering several, if not a number of square 
inches, frequently more or less clustered and 
appearing much like a mass of fungous mat- 
ter commonly seen under bark. 
Oligarces larve are similar in general as- 
pects, though we have yet to find them in any 
such large masses as described above. Elm 
bark containing this maggot gives little evi- 
dence on the inner surface of their presence, 
since these larvee appear to confine themselves 
mostly to the interstices of the bark. 
Biology.—tThe larvee of both genera repro- 
duce by pedogenesis in the fall and early 
spring. We have also observed this in the 
ease of Miastor in midsummer. Moisture and 
moderately cool weather appear to be espe- 
cially favorable. With these conditions we 
are inclined to believe that pedogenesis may 
continue indefinitely, since we have kept 
larve healthy and multiplying for nearly six 
months with nothing more elaborate than a 
moist piece of decaying wood clamped lightly 
to an ordinary microscopic slide. A larval 
generation appears to occupy about 3 to 3144 
weeks, though it is evident that much depends 
upon moisture, food and temperature. We 
were fortunate in the case of two larv to wit- 
ness the development of the egg in the ovary, 
its gradual separation therefrom by fission 
and the growth to an individual nearly ready 
to escape from the mother larva. This entire 
process occupied about three weeks. The de- 
velopment of the embryo is at the expense of 
the mother, the young absorbing their nour- 
ishment from her. Pulsations in the mother 
larva continue so long as a fragment of the 
dorsal vessel remains; in one specimen observed 
the dorsal vessel of the mother larva was rup- 
tured in the vicinity of the sixth body seg- 
ment and the free anterior portion continued 
violent pulsations and irregular wrigeglings 
till the next day, at which time the move- 
ments were much slower and by the following 
day had disappeared entirely. 
Reproduction by pedogenesis continues in 
SCIENCE 279 
the spring till just before the final changes to 
the adult, the larval colonies displaying a 
marked tendency to arrange themselves in 
groups and occasionally form rather striking 
combinations. This occurs, even in the case 
of colonies established under artificial condi- 
tions. At this season at least there is a 
marked tendeney toward uniformity in the 
production of larval generations, a consider- 
able proportion of the larva in any one colony 
containing embryos which may escape at 
about the same time and migrate to another 
location before establishing themselves. This 
removal from the exuvie of an earlier genera- 
tion clearly indicates a phytophagic habit and 
is presumably of value in avoiding natural 
enemies. In early May, 1911, embryos es- 
ecaped in large numbers from mother larvz, 
established a colony and in a few days showed 
a well-developed breastbone. The transforma- 
tion to the prepupa, characterized by a marked 
swelling and transparent condition of the an- 
terior body segments of the larva, occurred 
shortly, they remained in this condition two 
to three days and then changed to the pupa, 
a stage lasting about six days. ‘These small 
midges appeared in enormous numbers in our 
breeding jars during the late morning hours, 
namely, from about 9 a.M. until noon, the 
midges swarming over the sides of the jar and 
behaving much like minute ants. There is 
comparatively little tendency to take wing. 
This may continue for several days and the 
midges may appear in smaller numbers for a 
period of several weeks. Larvez collected in 
the Adirondacks did not produce midges till 
in early August. There was a marked pre- 
ponderance of one sex in rearings from a 
breeding jar one day, followed by an approxi- 
mate reversal subsequently. This was not 
sufficiently marked so that we felt justified in 
attempting to deduce any general rule. The 
abdomen of the female contains four to six 
large eggs, each nearly as long as the ab- 
domen. They appear to be well developed 
and are probably deposited shortly after the 
appearance of the midges and the pedogenetic 
generations commenced wherever conditions 
are favorable. 
