46 E. H. STRICKLAND 
1) are four-jointed, joints 1 to 3 being sub-equal, the fourth 
joint small and conical. The labium (figs. 6 and 7) has large 
swollen lateral teeth, and the central tooth is large and prominent 
while the intermediate teeth are small. On the ventral surface 
there are usually three strong setae in a row, and two smaller 
basal setae. The number and position of the setae, however, 
as in all species examined, are inconstant characters. The man- 
dibular bristles (fig. 3) are not very pronounced. The maxillary 
palpus is long and slender (fig. 5). The head capsule is never 
uniformly dark all over; when freshly moulted it is almost white, 
with a darker median line and dusky latero-basal areas (fig. 2). 
These latter fuse with one another till the greater portion of 
the basal two thirds of the capsule is of a deep brown color (plate 
5, fig. 1). The thorax and abdomen are greenish gray to brown. 
The apex of the abdomen is swollen and of a lighter color ven- 
trally. On each side of the swollen portion is a distinct dorso- 
lateral longitudinal furrow. The gills are simple and trilobed. 
Pupa: plate 1, figs. S and 9. This is 3 mm. long, chestnut 
brown, turning to black when mature, with four-branched res- 
piratory filaments (fig. 9). The dorsal surface of the posterior 
margins of the fourth and fifth abdominal segments have eight 
anterior curved, small, brown hooks. Usually no other segment 
bears traces of dorsal hooks but the sixth occasionally bears two 
or three. Ventrally segments 5 to 8 bear at least one pair of 
obsolete hooks on the posterior margin, and usually there are 
traces of a second pair of hooks on some of the segments. 
Cocoon. This is formed of rather coarse gray silk and does 
not completely enclose the pupa. It is of the wall-pocket type 
and is usually found singly, attached to stones or dead leaves. 
The pupa of this species is of especial interest, because only 
two other pupae have been described in which the respiratory 
filaments are only four branched. One of these is a European 
and the other a South American species recently described by 
Lutz 3(-10)2 
* Since the above was written Forbes (’12) has described the pupa of a new 
species §S. johannseni, found in the Illinois River, in which the respiratory 
filaments are four-branched. 
