702 LauRA FLORENCE 
and according to Nuttall is not present in Pediculus. Cummings (i916: 
260) has described a somewhat similar condition in Linognathus limnotragi 
Cummings in which the parameres . 
are of aremarkable type. Proximally they are broad blade-like pieces which meet each other 
(but do not fuse) beneath the mesosome in a fairly long median groove, then dorsally wrap 
themselves around the mesosome lying between them, forming a kind of sheath, from the 
end of which the penis projects, and, like the somewhat narrower distal ends of the parameres, 
curls up dorsalwards. 
The parameres are two strongly chitinized regions on the lateral walls of 
the dorsal lamella of the basal plate, and articulate anteriorly with its lateral 
processes in the region of the seventh abdominal segment (Plate LXIV, 
1, 2, 3, and 5). They are boat-shaped structures, with the keel external 
and lateral, and can be seen through both dorsal and ventral aspects. 
Distally they almost meet on the median line and proximally they diverge. 
The distal points appear to be less strongly chitinized than the remainder 
of the structure. In feeding experiments males approaching females 
were frequently seen to protrude and withdraw the parameres. 
The vesica penis (preputial sac of Mjéberg, mesosome of Cummings), 
when lying within the body, rests within the upper lamella of the basal 
plate, its walls are thrown into folds (Plate LXIV, 1 and 3), and its anterior 
part is invaginated within the more posterior part. When ejected (Plate 
LXIV, 3 and 4) it passes backward and slightly downward for about half 
its length, when it bends slightly upward again. It is from one-half to 
three-fourths of a millimeter long and at its widest posterior part is approxi- 
mately half as wide as its length. At its distal end on either side, directly 
on the median lateral line, are two small lobes covered with teeth, as is 
the whole sac with the exception of an area on the ventral surface near 
the proximal end. The thin, smooth wall of the sac surrounds the penis 
like a sheath for one-half of its length from the point of branching to the 
tip. It points directly dorsad. At its distal end the sac appears to be 
continuous with the basal plate. Above the copulatory apparatus and 
between it and the anal opening is the pregenital fold. No postgenital 
fold is present, unless the dorsal and ventral lamellae of the basal plate 
be considered as forming such. 
The penis is a strongly chitinized tube made up of two half-tubes closely 
apposed to each other (Plate LXIV, 1 and 4). It les within the vesica 
penis, its posterior pointed end turned toward the canal between the para- 
meres, and its anterior part, into which the ejaculatory duct passes, in 
