344 STEPHEN G. RICH 



loose bags filled with fatty cells and tracheae. The tracheae 

 passing to these fatty plates are branches from the dorsal trunks 

 only, but they are larger than those in the other Zygoptera dis- 

 cussed, and branch extensively on reaching the bags. 



Whether or not this be a respiratory organ I cannot say. It 

 conies the closest of any form outside the Anisoptera to the 

 longitudinal folds which I found in so many Aeschnidae. The 

 presence of fat, tracheae, and a thin epithelium over all comes 

 close to some of the details of anisopteran gill structure. The 

 rectum of Calopteryx resembles the intestinal ampulla of Agria, 

 shown in figures 42 and 43. 



THE INTESTINAL ^AMPULLA OF ZYGOPTERA 



Careful dissection of the abdomen of a nymph of Argia 

 putrida reveals the structures shown in figure 42. The rectum, 

 as previously explained, offers nothing of interest. The end of 

 the intestine, just caudad of the Malpighian tubules, is expanded 

 into a large globular ampulla, on whose sides are three fatty 

 plates, to which tracheae pass. Two of the plates are laterodorsal 

 in position, and the third one midventral. Figure 43 shows the 

 ventral aspect of the ampulla. 



Each of these plates is supplied by a branch from the trachea 

 which passes to the Malphigian tubules; two branches, one from 

 each side, go to the midventral plate. The surface of each 

 plate is covered with a thin, tough epithelium, much like that 

 of the anisopteran respiratory folds or gills. Beneath this is 

 the mass of fat, among whose cells the tracheal branches pass. 

 I was not able to determine whether or not the tracheae loop 

 here as in the anisopteran respiratory organs. 



In Calopteryx maculata the same structure is present. I 

 have not observed this region in other species. The function of 

 this organ is unknown to me. I am inclined to grant it some 

 respiratory use, in view of the fact, well known and observed 

 by me, that Argia and other Zygopteran nymphs can live for 

 days without the external caudal gills. 



