AMERICAN NEUROPTERA. 127 



minute teeth. The ligula and mentum are cleft to considerable 

 depth, and on either side of the cleft is a small tooth flanked by a 

 series of very minute ones. The line, indicating the base of the 

 border of the ligula, which was observable in Lestes, is noticeable 

 here also. 



ZYCJOPTERA. 



Some very curious labia are to be found among the Zygoptera ; 

 they differ from the labia of the other groups, and vary greatly even 

 from one another. No single species can be chosen as typical of the 

 group, but they fall into four fairly well defined classes correspond- 

 ing to the subfamilies of which nymphs are at present known. 



Epallagin.e. - Bayadera indica (PI. V, Fig. 1) and Libellago 

 curta (PI. V, Fig. 2) present many points of similarity, both having 

 a well developed hook, while Bayadera has two and Libellago three 

 hooks beneath it, the lowermost of which is very blunt at the end. 

 The inner edge of the lateral lobe is in each case bordered with very 

 minute teeth. The margin of the ligula of each is convex and cleft, 

 the cleft in the case of Libellago being much deeper. The border 

 of the ligula is covered with very small teeth, and beneath are visible 

 traces of an obsolete suture, bearing at either end a well defined 

 tubercle. Below this line m Bayadera, on either side of the center 

 of the mentum, are two setigerous punctures, homologous, perhaps, 

 with the similar punctures on the labia of new hatched Libellulines. 

 The lateral borders of the ligula are covered with hairs. 



Vehtalin.e (Calopterygin/e). — Calopteryx maeulatus (PI. V, 

 Fig. 3), Heterina americaiia. (PI. V, Fig. 4-), Phaon sp. ? (PI. V, Fig. 

 6), and Neurobasis chineiids (PI. V, Fig. 5) are representatives of 

 this group. They are very different from the members of the group 

 just described. Tlie lateral lobes in all four species are very narrow 

 and show, underneath a very well developed movable hook, three 

 long sharp hooks, varying slightly in size and shape in the different 

 genera. In all four, one or more small spinules appear upon the 

 lateral lobe just before the movable hook. A series of po(jrly devel- 

 oped teeth appear upon the inner edge of the lateral lobe in all ex 

 cept the Phaon. In Heterina and Phaon the cleft in the mentum 

 is of moderate depth and oval in shape, but the ligula is so narrow 

 and the width of the cleft is so great that the strip on either 

 side is exceedingly narrow. A small seta appears on either 

 side of the cleft about half way to the bottom. In Calopteryx and 



TKANS. XM. ENT. SOC. XXX. MAY. 1904. 



