418 MORPHOLOGY OF THE ABDOMEN IN THE ODONATA 



The Lateral Thoracico-Abdominal Muscles (plate XXV, 

 figures 17 and 23, Ita). These originate on the furca of the meta- 

 thorax and insert on the anterior end of the first sternite. Thej^ 

 are heavy and widest at the anterior end. 



The First Auxiliary Sterno-dorsal Muscles (plate XXV, figures 

 17 and 23, fasd) are cylindrical or spindle-shaped bands which 

 originate on the posterior processes of the metathoracic furca 

 and insert upon the anterior end of the first abdominal tergite. 



The Second Auxiliary Sterno-dorsal Muscles are thinner bands. 

 They have an origin similar to the above mentioned muscles but 

 insert upon the anterior part of the second abdominal tergite. 



Dorso-ventral Segmental Muscles: — 



There is but one pair to each segment in Zygoptera. 

 The Anterior Dorso-ventral Muscles (plate XXV, figures 17 

 and 23, adv). These very small muscles pass vertically from 

 their origin on the lower edge of the tergum up to the under side of 

 the second sternal process. 



The Tergo-Sternal Genital Muscles (Transverse Genitals of 

 other authors) (plate XXV, figure 23, t?g). In Calopteryx the 

 males possess two pairs of these in the second segment ; one has 

 its origin above and in front of that of the Inferior Longitudinal 

 Tergal Muscle and its insertion upon the side of the sternum 

 caudad of the origin of the Longitudinal Sternal. This may be 

 the Inferior Longitudinal Tergo-Pleural with its insertion moved 

 to the sternum and cephalad. The other has its origin just dorsal 

 to and in front of the first, and its insertion on the face of the 

 sternum anterior to the origin of the Longitudinal Sternal. It is 

 of uniform diameter. 



II. Anisoptera. Aeshninae 

 All of the work of this section was done upon Anax Junius and 

 Aeshna umhrosa. The differences between the two were very few 

 and slight: matters of size or minute variation in position. 

 The Alimentary Canal 

 (Plate XXVI, figure 25) 

 After passing the occipital foramen the digestive tube expands 

 suddenly several diameters. From the prothorax to the middle 

 or posterior part of the metathorax the size of the oesophagus is 



