ARTHUR DEWITT WHEDON 407 



the Ventral and the Lateral Sternal Thoracico-Abdominal Mus- 

 cles (plate XXIII, figure 8, vsta, Ista, Istah.). They seem also to 

 coincide with those of Aeshna as described by Wallengren. Mus- 

 cles Controlling the Anal Appendages and the Rectum are also 

 so nearly like those of Ledes and Aeshna as to need no description. 



Dorso-ventral and Oblique jNluscIes: — 



The Dorso-ventral Segmental Muscles (plate XXIII, figures 

 8, 9, 10, and 11) are very strongly developed as compared with 

 the Zygoptera, and are different as to their insertion. The}' are 

 found in all segments from the first to the ninth, and are strongest 

 in the sixth and seventh. In segments one, two, three, and four 

 they seem to be single, thick and somewhat flattened; from the 

 fifth to the ninth they consist of three muscles — a large fore one, 

 a smaller hind one, and a middle and slightly internal one, which 

 is very nmch the weakest. They run vertically parallel with one 

 another except the central one which is a trifle oblique. The 

 insertion of the group occupies the greater part of the pleurite 

 (epimerite) in all but segments one and nine where it is upon the 

 sternum. The origin covers a broad lateral line on the tergum, 

 the central division being a little higher up than the other two. 

 The condition is the same in Aeshna. 



The Dorso-ventral Oblique Intersegmental Muscles of the 

 Aeshnidae (plate XXIII, figures 8, 9, 10, and 11, dvo) take the 

 place of the similar, but segmental, muscles of the Zygoptera. 

 They are present in all segments but the tenth, and run from the 

 anterior-lateral corner of the pleurite and the suture-fold of one 

 segment to a point on the anterior suture-fold of the next seg- 

 ment receding, just beneath the lateral corner of the Secon- 

 dary Longitudinal Tergal Muscle. They are broadest and flat- 

 tened at the u per ends and nearly cylindrical at the lower ends, 

 and are powerful muscles. They pass interior to the Dorso- 

 ventral Segmental Muscles. 



Transverse Muscles: — 



These seem very similar in Anax and Aeshna. 



The Subintestinal Transverse Muscle (plate XXIII, figure 8, 

 str; plate XXII, figure 6, str) is a heavy, spindle-shaped, though 

 slightly flattened muscle, the ends of which attach to the pleurites 



TRANS. AM. ENT. SOC, XLIV. 



