324 bulletin: museum of comparative zoology. 



ms'phg.^. Since the infolding hypodermis of the pupa carries witli it 

 the attachments of the anterior end of this muscle, the musculus 

 metanoti is attached in the imago to the posterior face of the mcso- 

 phragma. The metaphragma {mfphg.) is formed by a similar infolding 

 at the posterior margin of the somite', and consequently the posterior 

 end of the muscle is attached to tlie anterior face of this ingrowth. 



Musculus lateralis metanoti of Luks. 

 (Pretradeur de Vaile of Straus-Durckheim ; latero-dorsal of Amans.) 



This muscle is present in the larva (Plate 1, Figure 1, Z. mf'nt.) a.s 

 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 

 fi,bres do not stretch through the full length of the nietathorax, but 

 extend from a suture (Plate 1, Figure 2, suf. a.) — which probably 

 represents the posterior boundary of theprescutum — posteriorly and later- 

 ally to the posterior edge of the somite. In the JW^ (Figure 2, I. mfnt., 

 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, I. mfnt.) 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, /3, y, 8, c, ^, rj) are, 

 in general, those of the deeper layer, and all of them except a extend 

 the full length of the somite. In the young jm^ja (Figure 2, a, /?, y, 8, 

 c, ^, 77) 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 doi'so-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 l) ; 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. : 



