BREED: METAMORPHOSIS OF THE MUSCLES OF A BEETLE. 327 



(Plate 1, Figure 3, exi. al.pa. mfthx.) of two fibres, which extend from 

 the posterior lateral surface of the raetathorax ventrally, and a little 

 toward the median plane to attach to the posterior edge of the 

 leg, very close to the attachment of the second flexor of the coxa. At 

 this stage its only function is that of flexor of the coxa. In i\iQ pupa 

 (Plate 2, Figure 5, ext. al. pa. mt'thx.) a fusion of the two fibres takes 

 place, and a very considerable shifting of position. The attachments of 

 this muscle in the imago (Plate 4, Figure 9, ext. al.pa. mt'thx.) are, dor- 

 sally, to the small cupule, which is placed immediately posterior to the 

 large cupule, and, ventrally, to the ventral surflice of the coxa just lateral 

 to the insertion of the second flexor of the coxa. 



ReJaxator extensoris alae of Luks. 

 {Releveur de la grande cupule of Straus-Durckheim ; dorso-preaxillaire 



of Amans.) 



There is some doubt as to the larval condition of this muscle and the 

 few muscles next described ; this is due principally to their small size. 

 During pupal life, this muscle and the relaxator alae metathoracis are so 

 closely united as to be indistinguishable. In fact, there is little more 

 than a mass of tissue containing remains of larval muscle and having 

 about the position indicated in Figure 5 (Plate 2) by rlx. ext. al. and 

 rlx. al. mt'thx. Out of this mass are differentiated the two muscles men- 

 tioned above. In the imago the relaxator extensoris alae (Plate 4, Figure 9, 

 7'lx. ext. al.) is inserted on the edge of the large cupule to which the 

 extensor alae magnus metathoracis is attached. Its origin lies almost 

 directly dorsal to this point on the wing-bearing apophysis. 



Relaxator alae metathoracis of Luks. 

 (Relaxateur de Vaile of Straus-Durckheim ; muscles du tampon of Amans.) 



The attachments of this muscle in the imago (Plate 4, Figure 9, rlx. 

 al. mfthx.) are as follows. Its origin is on a small cupule placed near 

 the dorsal attachment of the musculus lateralis metathoracis anterior 

 (Plate 5, Figure 11, I. mt'thx. a.), from which it extends laterally, and 

 somewhat ventrally, to attach on the base of the wing. 



As to the larval condition of the two muscles last described (rlx. exf. 

 aL, rl.c. al. mt'thx.), it seems probable that they are derived from three 

 fibres. It is possible, and even probable, that the two fibres so marked 

 (Plate 1, Figure 4, rlx. ext. al. ?) give rise to the relaxator extensoris 

 alae of the imago, and that the other fibre (Plate 1, Figure 4, rlx. al. 



