breed: metamorphosis of the muscles of a beetle. 323 



the imago, are misnomers when applied to the muscle in its larval state. 

 Even though such misnomers may cause confusion, they are retained in 

 this paper because no better nomenclature is available at present. 



In the detailed description of the muscles, the order followed is : 

 (1) dorsal antero-posterior, (2) lateral dorso-ventral, and (3) ventral 

 antero-posterior. By this arrangement, the wing muscles of the imago, 

 both direct and indirect, are spoken of first. 



(1) Tlie dorsal antero-poderior group of muscles is shown in Figure 1 

 (Plate l), which is a view of the left side of the larval metathorax seen 

 from above (dorsal), anterior being up on the plate. Figure 2 is a 

 similar view of the pupal metathorax. In the upper portions of Figure 9 

 (Plate 4) and Figure 1 1 (Plate 5) is shown the same group of muscles 

 in the imago as they would appear when seen from the left side of the 

 thorax, after cutting away the lateral wall of the metathorax. 



Musculus metanoti of Luks. 

 (Abaisseur de Vaile of Straus-Dlirckheim ; dorsal of Amans.) 



The musculus metanoti is one of the most important of the indirect 

 wing muscles, since it functions as the principal depressor of the wing 

 in the imago. In the larva (Plate 1, Figure 1, mt'nt.) it exists as three 

 distinct muscles, extending from the anterior to the posterior boundary of 

 the metathorax. At this stage the three muscles do not even lie parallel 

 to one another. It is their subsequent history only which shows that they 

 constitute one imaginal muscle. Just before pupation, in a larva which 

 is no longer feeding, these three muscles show histological evidences of 

 metamorphosis, which will be described later. There is very little 

 change anatomically, till pupation, when there is a quite rapid shifting 

 of the attachments of the three muscles, caused by the unequal growth of 

 the hypodermis. In the pU2m (Figure 2, mfnt.) they still extend 

 throughout the entire length of the somite, but have changed their rela- 

 tive positions so that now they lie parallel to one another. In the older 

 pupa they grow in size until they touch each other, and in the young 

 imago (Plate 4, Figure 9; Plate 5, Figure 11, mt'nt.) they become so 

 united as to be almost indistinguishable. Each of the three original 

 muscles has divided lengthwise into from three to nine fibres, so that the 

 entire adult muscle is composed of about fifteen fibres. 



During pupal life thei'e is- formed an ingrowth of the hypodermis 

 along the dorsal portion of the suture between the meso- and metathorax, 

 and from this is formed the mesophragma of the imago (Plate 4, Figure 9, 



