184 THE AMERICAN NATURALIST. [VoL. XXXVI. 
be no doubt that this obscure and little-known fly is a factor of 
considerable importance in the ecology of such a situation. 
Immature Stages. — I now describe the larva and the pupa, 
and accompany the descriptions with drawings by Miss Maude 
H. Anthony. 
Larva.— Length 13-14 mm. ; diameter 1.5 mm. Body cylindric as far 
as the 9th abdominal segment, or with slightly greater depth in the thorax ; 
head well developed, exserted, about equal in length to the body segments, 
except the first, which is a third longer than the others ; there is a distinct 
Y-shaped suture on the top of the head; a pair of sete are inserted just 
before and another pair just behind the clypeal suture ; eyes wanting ; four 
setze on the epicranium each side, — two at the edge and one above and 
one below ; there are lesser setze on the maxilla externally. The lacinia 
of the maxillae and the mandibles are elongate pyramidal, with low teeth on 
their truncated apices. There are two pairs of thoracic and eight pairs of 
abdominal spiracles: the foremost is situated at the rear of the prothorax 
and is larger than those following, except the last ; the second pair is at the 
front margin of the metathorax; the next seven pairs are just before the 
middle of abdominal segments 1-7 ; those of the 9th abdominal segment 
are very large and each is divided by a median groove. Each of the middle 
body segments is completely encircled by a row of about a dozen tubercles, 
which is slightly oblique upon the sides and in which the dorsal tubercles 
are usually longer than the ventral, and there are a few tubercles out of 
line at the sides in the vicinity of the spiracle ; on the 1st segment behind 
the head there is another row of eight tubercles, on the dorsum between 
the spiracles, and on this segment the tubercles are all longest at the sides ; 
on segment 8 of the abdomen the dorsal tubercles are more elongate and 
the ventral ones more reduced ; segment 9 is depressed conic, tapering 
posteriorly, with the large spiracles inserted in anterior emarginations of 
a brownish, chitinous, saddle-shaped plate, which covers most of the dor- 
sum of the segment; behind this plate arise two pairs of filaments (elon- 
gate tubercles), the median pair as long as the segment is thick, the external 
pair a third shorter. 
Skin granulate, amd invested with adherent dirt particles. 
Pupa.— Length 7.5 mm. ; breadt h of thorax 2.1 mm., of abdomen 
1.5 mm. Body iiss, whitish, with low appressed head, short, thick 
thorax, and straight abdomen whose sides are parallel except at its abruptly 
tapering apex. 
. Head fiat, with short antenna cases which extend hardly more than 
halfway across the eyes, with well-marked paired jaw cases, and with 
an ocellar tubercle at the rear of the head above, low in the male, high 
ah poniienpln el eee E: 
eyes). 
