682 LauRA FLORENCE 
floor of the sheath. Posteriorly the diameter of the sheath decreases, 
until in the region of the rami of the piercers it surrounds them closely. 
The piercers and the salivary duct 
The piercers resemble long-handled two-pronged forks, having the 
prongs, which are 0.23 millimeter in length, situated posteriorly. They 
are long and slender, and lie free in the anterior part of the sheath, while 
their posterior forks are imbedded in tissue, completely filling the lumen 
so that sheath and piercers form a-compact mass. This tissue extends 
forward among the piercers in two slender, pointed prolongations. A 
similar arrangement of tissue has been described by Sikora (1916:38) 
in the clothes louse. The dorsal element consists of two half tubes which 
in sections appear like two brackets having their contiguous edges fused 
(Plate LXI, 2). Posteriorly these become flattened, and after forking 
attain a width of 0.25 millimeter at their widest part, whence they narrow 
again and finally end in two ligament-like bands which come together 
at the point of their insertion in the posterior wall of the sheath. Anteriorly 
the two halves do not lie side by side, but are curved upward and toward 
each other so as to form a tube. The ventral aspect is made up of two 
parts, a dorsal and a ventral, which are closely apposed to each other 
but can be pulled apart without injury to either after being dissected 
out from the surrounding tissue. The posterior rami of the dorsal part 
are wider than those of the dorsal element of the piercers, and are some- 
what different in shape (Plate LX, 6). They do not become flattened, 
and in sections appear subcircular. A small lateral process is given off 
from each shortly before they unite to form the piercer,’ which is a moder- 
ately heavily chitinized groove with more delicate edges spreading out 
flangelike over the edges of the ventral part of the piercer (Plate LXI, 1). 
The latter is also a canal-like structure (Plate LXI, 2), and its posterior 
rami are imbedded in the floor of the sac. Both parts of the ventral 
element of the piercers are bilobed at their proximal end. The lobes of 
the ventral half are somewhat wider apart than those of the dorsal, and 
both are finely serrated. | 
The salivary duct lies between the dorsal and ventral elements of the 
piercers, and at its posterior end is dilated in the form of a slender bulb 
which can be seen lying between the rami of the dorsal element, to the 
ventral surface of which the duct is attached through part of its length 
