ARTHUR DEWITT WHEDON 401 



is a good example of the earlier investigations of this Aeshnid, 

 while such work as Matula's in 1911 and Wallengren's in 1914 

 offer the best basis for further work. None of these papers treat 

 of the complete anatomy or physiology of this species: Dufour 

 considers the nervous, respiratory, circulatory, and digestive 

 systems; Amans (1881) the digestive and respiratory systems; 

 Viallanes (1884) gives a brief laboratory synopsis of the external 

 features, the mouth parts, alimentary canal, main tracheal trunks, 

 and the nerve chain; Matula and Wallengren are interested in 

 the nervous system and the respiratory movements and so touch 

 upon the muscles and the skeleton. 



The following results were obtained from the dissection of Anax 

 Junius. Specimens of all sizes were available in numbers. A few 

 were collected in the act of moulting and furnished very trans- 

 parent material. Part of the dissection was carried out in 70 

 per cent alcohol without staining, much more after staining, and 

 some study was made of parts mounted in balsam. Constant 

 dissection is, however, the method to be advised, especially upon 

 the sternal and tergal muscles. 



The Alimentary Canal 

 (Plate XXII, figures 5 and 6, al.) 



Compared with the digestive tract of the Zygoptera that of the 

 Anisoptera is more complicated. The addition of respiration to 

 the functions of the rectum is partly responsible for this. The 

 three general divisions arc much the same — fore gut, mid gut, and 

 hind gut— but some of the regions are more specialized in their 

 activities. 



The Oesophagus runs back through the head, turns dorsad for a 

 very short distance after passing the occipital foramen, turns 

 again toward the axis of the thorax and rapidly enlarges as it 

 traverses the prothorax, mesothorax and about half of the meta- 

 thorax. Here it turns ventrad and constricts slightly, but im- 

 mediately expands again to form the large oval crop which oc- 

 cupies the first two segments of the abdomen. The walls of both 

 these divisions are marked b}' longitudinal wrinkles. The ac- 

 companjang figures were drawn from a quite f ully^rown moulting 

 larva, the digestive tract of which was distended with air. 



The Gizzard lies normally in the anterior part of the third 

 segment, where the ventriculus is moderately invaginated by it. 



TRANS. AM. ENT. SOC, XLIV. 



