NO. .12 FLYING APPARATUS OF BLOW-FLY — RITTER 27 



the abductor primus, is delta-shaped, arises from the rostral and 

 ventral border of the parapleurum, and is continued in a tendon 

 which extends under the parapterum, traverses the foramen postalare 

 and is inserted -on the anterior border of the wing-joint, probably 

 close to the depression of the processus pteralis alse 3. Lowne's 

 view, that this muscle is attached to the parapterum, is erroneous. 



8. The pronator alee (text figs. 6, 7, pi. 11, fig. 30; mp). This 

 muscle is similar in shape to the abductor secundus, but much more 

 slender. It arises from the ventral border of the parapleurum, 

 passes, together with the abductor secundus, below the parapterum, 

 and is continued into a tendon which passes through the foramen 

 prsealare. Its insertion is similar to that of the abductor secundus. 

 The exact spot of attachment could not be determined. 



9. The musculus gracilis (text fig. 6, pi. 11, fig. 34; w^-). This 

 muscle is small and oval. It arises from the parapterum and is 

 continued in a delicate tendon which is attached to the processus 

 dactyloformis of the scutum. 



10. The musculus anonymus (text figs. 6, 7, ma). As the name 

 implies, I was unable to determine with certainty the points of 

 insertion and the function of this muscle. It covers the episternum, 

 is very deUcate and appears to be somewhat rudimentary. 



B. PHYSIOLOGICAL PART 

 Methods of Investigation 



The experimental study of the movements of the wings is ren- 

 dered difficult by the small size of the latter and by the complicated 

 nature and rapidity of the former. 



Three methods have been employed for investigating the nature 

 of the wing-movement. The oldest of these is the optical method, 

 which has been employed particularly by Pettigrew and by Marey 

 (1886, p. 93). This method is based on making the tip of the wing 

 especially visible by attaching to it a bit of gold leaf and then ex- 

 amining the bright line produced by this glittering point when the 

 insect is held in a beam of strong light and induced to move its 

 wings. The bright line then seen has the shape of the figure 8. 

 Another method is the kymographic, which was likewise employed 

 by Marey. When using this method the insect is held near a re- 

 volving blackened cylinder in such a manner that the moving tips 

 of its wings describe points or curves on it. Since the tips of the 

 wings move in spherical surfaces, they either — when the insect is 



