404 MORPHOLOGY OF THE ABDOMEN IN THE ODONATA 



The Muscular System 

 (Plate XXIII, figures 8 to 12) 



As stated above, the papers of Matula (1911) and of Wallengren 

 (1914) are the only ones that are concerned with the muscles of 

 the abdomen of the Anisopterous larva. The former of these is 

 very superficial from the side of anatomy, as only the larger Sets 

 of muscles are figured or described. Wallengren has not limited 

 himself to the respiratory muscles, but has undertaken to dis- 

 cover and systematically describe all the abdominal muscles of 

 the larva of Aeschna grandis. His figures are excellent. His 

 nomenclature, derived from earlier workers on insect muscles, 

 is largely followed in the present paper; the Latin form is not 

 used, however. 



The Aeshnid larva is the most complex of those of the various 

 subfamilies: especially is this true of the muscles. Onl}^ such 

 details as were not described in the previous section on Lestes will 

 be given here. 



Segmental Muscles of the Stern^im: — 



The Primary Longitudinal Sternal IVIuscles (plate XXIII, 

 figure 8, pis.) are found in segments two to eight inclusive. They 

 differ from those of the Zygoptera in diverging caudad and in- 

 creasing in size toward the posterior segments. In segments 

 four to seven inclusive a longitudinal division has occurred giving 

 rise to the following pair: 



The Lateral Primary Longitudinal Sterno-pleural Muscles 

 (plate XXIII, figure 8, Ipsp). These have their origin on the 

 posterior side of the anterior suture-fold lateral to the origin of 

 the primary Longitudinal Sternal Muscles in each segment. 

 They run caudad and laterally over the posterior suture narrow- 

 ing as they go, and insert upon the inner anterior portion of the 

 pleurite (epimerite). Wallengren considers these two muscles 

 but two portions of the same muscle — the Primary Longitudinal 

 Sternal — a median and a lateral. However, as they do not have 

 the same insertion and as their origins are not at the same point 

 but side by side, it would seem clear that they are two different 

 muscles at present, whatever may have been their origin. 



