182 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
thorax. Below in front and generally along the sides of the body 
an irregular space is left between body and shield. This space is 
filled with air (Hurst) and into it the recurved apices of the mouth- 
parts and the folded legs project. 
When the dermis shrinks away from the cuticle a few hours after 
pupation, the various trophi become oval or cylindrical tubes and 
remodeling of the imaginal forms is possible. The mandibles, max¬ 
illae, and maxillary palpi — these last occupy the same cuticular 
sheath as the maxillae — undergo the least modification. In male 
pupae the mandibular sheath was empty by the end of the first day 
of pupal life. During a variable period of not less than ten hours, 
the labrum remains circular in section. Then its ventral face 
becomes infolded, and through differentiation of the furrow, the 
proboscis canal or so called epipharynx is formed (pi. 14, fig. 24, 
}ic). The labium retains a cylindric or oval cross section until 
near the end of the first day of pupal life. Then the dermis 
of the mid-dorsal face is either elevated as a low crest or prolifer¬ 
ates and thickens (pi. 14, fig. 24, hyp). In both sexes cells appear 
in the cavity of the labium beneath the altered Avail and ultimately 
build the salivary gutter. These cells probably arise by invagina- 
tion or migration from the modified area above. After they appear, 
the labium of the male pupa loses the mesial differentiation and 
quickly moulds itself to the imaginal form, but with the female 
pupa the ridge or thickening finally separates from the labium as the 
hypopharynx (pi. 14, fig. 25). I did not succeed in obtaining sec¬ 
tions which showed the actual separation. After disassociation, 
both labium and hypopharynx quickly attain the imaginal struc¬ 
ture. 
The fore gut. — Since the mouthparts of the pupa are in close 
contact with one another, it cannot be said that the alimentary canal 
is lengthened by the addition of a proboscis canal so long as the 
dermis lies against the cuticle of the stylets, and although repre¬ 
sented by the intracuticular spaces betAveen labrum and labium 
after their dermis has parted from the cuticle, yet the canal is not 
actually formed until the ventral Avail of the labrum is invaginated. 
If a new-formed pupa be examined, the fore gut will be found 
empty and clean. The buccal cavity is closed by the collapse of 
its walls, except at the posterior end, beneath the shalloAv dorsal 
diverticula which represent the fiabellae and epipharynx (pi. 15, 
