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 unable to find more than one flexor of the wing 
in Dytiscus. Asa 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-Dirckheim and myself (Plate 4, Figure 9, jl. 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. 
(Abaisseur 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, ms’fur. 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. tf. 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 (ms’fur.) in the imago. 
Musculus lateralis processus inferioris mesophragmatis. 
In the Jarva, this muscle (Plate 1, Figures 3, 7. pre. if. ms’phg.) is a 
simple fibre, whose dorsal end attaches to the suture between the meso- 
