K!:S!MK;.\TI(i,\ o/ \IES<)(.0M/'III ^■ 



4;^' 



The res])irat()ry rectum serves also as a swimming (jrgan. 

 Ilv ejecting its contents suddenly, the nymi)]i ijroj^els itself fur- 

 ward in a jerk\ fasliion. This may easily be seen in the nvmiih 

 of any dragon-tly. if i)Ut into clear water and disturbed. 



Jl is ■-omewhat interesting to compare tliis rectum of Mesu- 

 cjouipJius with that of other dragon-fly nymphs. Except for 

 details of di<tributi(^n of the tracheal branches, there is no great 

 difference Ijetwccn the external ai)])earance of the rectum in all 

 the species of dragon-fly tlius far studied. Tlie Ij'bellulid;c lad. 

 the anal canal : their rectum narrows al)ru])tly to the valve. 



The differences between the nym])hs of dift'erent species an,: 

 found in the cliaracter of the gills. The accepted genera seem 

 to agree with the \ariations in gill-character. 



In the .Aeshnidce. we lind much variation in gills. Tlie 

 (jomphinie have, in the main, gills (|uite different fn^tu those 

 of Mesoi/onipluis. Hagcnius. iioinpluts. and Ophiogoniphits, 

 genera of luu'opc and North America. ha\e. instead of fol<K. 



c- 



tufts of villi tilled with l(,)op> of tracheae. Lanthus, of Xorlli 

 America, has folds almost identical with those of Mcso(jomphits. 

 Kis. i<;i,^. rejjorts iov ■ (ioinphits piilcliellus of luirope and 

 for Oiiyc/iof/onip/ius a combination form, with \illi on the crests 

 of the folds. This, however, 1 did not find in the North 

 American species of (jouipliiis, which I studied; nor have ])re- 

 vious workers ifotmd it. In the Aeshninse there is also^ varia- 

 tion, Acshiia. Basiacshna, Boycria, have folds much like Mcsr- 

 (jompluts has, but with much enlarged buttress folds, which are 

 true buttresses for the main folds. Anax had villi. Ijut thev 

 are short and on the crest of small longitudinal folds. Cordjdc- 

 (jaslcr, the one genus of the ( )ordulegasterin;e. has folds like 

 Aeslina. This is rejjorted for several Xeai"ctic s])ecies by dif- 

 feren.t workers. 



The Libellilud;e I have discussed in my ])revious ])a]xM'. 

 Figure 8 shows a gill of Ortlicfruiii sp. found in the 

 Amanzimtoti River. There are from 200 to 360 gills in tlie 

 recttnn, the nimiber \arying with the species. Earlier writers. 



