SOFT PARTS AND MECHANISM OF THE PROBOSCIS. 405 
The so-called salivary reservoir in Blatta is identical with the 
larval sericterial gland of Musca in form and structure, and 
this is replaced in the imago of Musca by the tubular lingual 
gland; whilst the lobulated glands of Blatta do not differ 
from the racemose glands of Volucella and Syrphus, which co- 
exist with a tubular lingual gland in the imago of these insects. 
In the imago of the Blow-fly two pairs of glands exist, which, 
as they discharge their secrétion either on the lips of the 
proboscis, labial glands, or into the mouth, lingual glands, may 
fairly be classed as salivary. 
Kraepelin describes a third pair which discharge their 
secretion into the pharynx, but I have been unable to satisfy 
myself that any such glands exist in Calliphora Erythrocephala; 
they may be present, however, in some allied insects, such as 
Lucilia and Sarcophaga. 
The Labial Glands (PI. VI. and Fig. 31,5 g) are situated at the 
distal extremity of the haustellum, one on either side of the 
poculum. The ducts of these glands run parallel with the 
pseudo-trachez, and terminate in nipple-like orifices between 
them; four or five of these are seen between each pair of 
pseudo-trachee (Pl. XXIII.). 
Each gland consists of a sac lined by large columnar cells 
with a distinctly rodded structure; these cells are similar to 
those of the sericterial (lingual) glands of the imago. I have 
been unable to detect any cellular lining to their branching 
ducts, which are usually distended with a coagulable fluid. 
Kraepelin believed that these glands open by short wide 
ducts into the poculum, an opinion which I formerly held ; but 
I have so frequently traced the ducts to the nipples between 
the pseudo-trachee that I can no longer agree with Kraepelin. 
Further, Kraepelin regards these nipples as sensory organs, a 
view which is not supported by any of my sections. I have 
been quite unable to trace nerves to these papillz. 
The purpose of the labial glands is clearly to keep the surface 
of the sucker moist with a tenacious viscid fluid which differs 
entirely from the clear watery secretion of the lingual glands. 
The Lingual Glands or Sericteria.—These glands replace the 
