breed: metamorphosis of the muscles of a beetle. 329 



of Melolontha, though possibly the three flexors of Thymalus are re- 

 spectively homologous with the three of Melolontha. 



Luks states that he is uuable to find more than one flexor of the wing 

 in Dytiscus. As a matter of fact, the muscle which he has described as 

 the flexor of the wing is the fourth flexor of the posterior coxa. This 

 may be seen in his own figure (Tafel 23, Figur 12, fa.), where this 

 muscle is shown attaching to the lateral edge of the posterior coxa, and 

 occupying a position exactly similar to that of the fourth flexor of the coxa 

 as shown by Straus-Diirckheim and myself (Plate 4, Figure 9, fix. cox. 

 mt'thx. 4). This conclusion is corroborated by the dissection of Colym- 

 betes, where not only the fourth flexor of the coxa, but also the three 

 flexors of the wing are found occupying their usual positions. Inas- 

 much as the muscles of Colymbetes are almost exactly identical with 

 those of Dytiscus, it is certain that Luks overlooked the flexors entirely. 



The conditions in Synchroa and Bruchus are much like those in Thy- 

 malus, except that in both of these beetles the second and third flexors 

 are fused into a single muscle. The third flexor is divided in both cases 

 into three parts, which attach on the base of the wing by a common 

 tendon. 



The muscles described thus far are all muscles of flight, acting either 

 directly or indirectly on the wing. Those now following have very little, 

 if any, action on flight. 



Musculus mesofurcae dorsalis. 

 (^Ahaisseur du diaphragme of Straus-Diirckheim ; musculus furcae dor- 

 salis of Luks.) 



In the larva (Plate 1, Figure 3, ms'fur. d.), this is one of the muscles 

 which extend dorso-ventrally along the suture between the meso- and 

 metathorax. It attaches laterally, and extends to a ventro-lateral posi- 

 tion. The position of this muscle changes very little during pupal life 

 (Plate 3, Figure 7, vis'/ur. d.), but there are ingrowths of hypodermis at 

 both dorsal and ventral attachments. The dorsal ingrowth forms in the 

 imago the inferior process of the mesophragma {pre. if. ms'phg.), to the 

 tip of which this muscle (Plate 5, Figure 11, ms'fur. d.) attaches. The 

 ventral attachment is to the ventral ingrowth which forms the meso- 

 furca (jns'fur.) in the imago. 



Musculus lateralis processus inferioris mesopTiragmatis. 



In the larva, this muscle (Plate 1, Figures 3, l.prc.if.ms'phg.) is a 

 simple fibre, whose dorsal end attaches to the suture between the meso- 



