324 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
ms’phg.). Since the infolding hypodermis of the pupa carries with it 
the attachments of the anterior end of this muscle, the musculus 
metanoti is attached in the imago to the posterior face of the meso- 
phragma. The metaphragma (m#’phg.) is formed by a similar infolding 
at the posterior margin of the somite, and consequently the posterior 
end of the muscle is attached to the anterior face of this ingrowth. | 
Musculus lateralis metanoti of Luks. 
(Prétracteur de Vaile of Straus-Diirckheim ; lateéro-dorsal of Amans.) 
This muscle is present in the larva (Plate 1, Figure 1, l. mint.) as 
two, or occasionally three, fibres. When three fibres are present, the 
two more lateral are always closely approximated, as in the case figured ; 
this, then, is a simple doubling of the more usual single fibre. These 
fibres do not stretch through the full length of the metathorax, but 
extend from a suture (Plate 1, Figure 2, swt. a.) — which probably 
represents the posterior boundary of the prescutum — posteriorly and later- 
ally to the posterior edge of the somite. In the pupa (Figure 2, l. m#’nt., 
drawn from an animal which had but two fibres in the larva) these two 
or three fibres become approximated, and in the old pupa fuse to form a 
single muscle. In the imago (Plate 4, Figure 9, /. mé’nt.) the attach- 
ments of this muscle are, anteriorly, to the anterior portion of the scutum, 
and, posteriorly, to the postscutellum and metaphragma. 
The muscles which degenerate (Plate 1, Figure 1, a, 8, y, 6, ¢, & 7) are, 
in general, those of the deeper layer, and all of them except a extend 
the full length of the somite. In the young pupa (Figure 2, a, £, y, 8, 
e, £7) they are still present, showing, however, even anatomical evidences 
of degeneration. They are very irregular in outline, and do not extend in 
a straight course from origin to insertion, because they are greatly re- 
laxed. No traces of them can be found in old pupae and imagines. 
(2) The lateral dorso-ventral group of muscles of the larva is by far 
the most important of the three groups, since from it are developed 
nearly all of the muscles of the metathorax of the imago. This group is 
shown in lateral aspect for the larva in Figures 3 and 4 (Plate 1) ; for 
the pupa in Figure 5 (Plate 2) and Figure 7 (Plate 3), and for the imago 
in Figure 9 (Plate 4) and Figure 11 (Plate 5). Figures 4, 5, and 9 show 
the more superficial lateral layer of muscles in their respective stages. 
The group embraces no less than twenty-seven muscles on each side of 
the metathorax : viz. : 
. _— 
