114 Bulletin Wisconsin Natural History Society [Vol. 13, No. 2 
tory, or rather looping movements at the bottom of the vessel. 
It is of interest to note here that some of the larvae, especially 
younger ones, appear to be able to hold themselves to the sur- 
face film in a vertical position for a considerable length of time, 
varying from a few minutes to as much as an hour. Of course, 
disturbance will force them to drop to the bottom. This method 
of suspension from the surface is again comparable to that of 
Dytiscid and Hydrophilid larvae; obviously it serves the same 
purpose — respiration. 
THE PUPA 
Length, 1.7-2. 7 mm., exclusive of respiratory tubes. 
Color uniform pale brown. Respiratory tubes somewhat shorter than 
the distance between their bases, consisting of a brief wrinkled basal por- 
tion, and a wider smooth distal portion which is about six times the length 
of the basal part. 
Occipital crest between the tubes slightly roughened. 
Pigment spots and antennal spicules black; the pigment spots are 
placed at the lower end of the zone marking the extent of the future com- 
pound eyes; the antennal spicules are present between the eyes above the 
clypeus. Antennal sheaths each side reaching slightly beyond the line 
of the rhinarium. 
Wing sheaths and leg sheaths reaching beyond the base of abdominal 
segment two ventrally. 
Abdomen with segments two to six with two poorly defined annuli 
each, best recognized along the later margins. Each annulus marked by 
a ridge, the anterior nearly basal, the posterior subapical. The subapical 
ridge with small black sprnes interspersed with occasional setae, which 
seem to have a fairly regular arrangement, but which often are very diffi- 
cult to recognize. The basal ridge with four longer ventral spines, two 
lateral, and four dorsal spines, absent from segments one and two; each 
spine accompanied by a minute spine basal to the longer one. 
Caudal segment ending in two pairs of spines. The ventral pair is the 
larger pair, is longer than the dorsal and extends straight out in a line 
with axis of the body. To this position the dorsal pair are nearly per- 
pendicular, that is, they seem to arise from the ventral pair with a sharp 
curve, turn at right angles to the ventral pair, and end in two sharp black 
somewhat approximated spines. The ventral spines are widely divergent 
at their tips. 
I am unable to separate the pupa of P. cinerea from its relative 
P. domestica because of the insufficient description of the latter. 
However, since the pupal life is hardly longer than two or three 
days its positive identification becomes of less importance. 
