116 HORTENSE BUTLER. 



Fig. 13). Ill this the hook-like character of the movalile hook has 

 become apparent and teetli have been developed along the end of 

 the lateral lobe and two upon tlie inner edge. Teeth have devel- 

 oped in a double series at the base of the cleft between the two 

 divisions of the nientum, and immediately above the lower series is 

 a marked indentation which appears to be the beginning of a suture 

 dividing each lobe of the developing ligula into two parts. The 

 shifting which these parts undergo in forming the ligula as it appears 

 in the nymph will be discussed later. 



The earliest of the nymphal labia (PI. lY. Fig. 8) shows com- 

 paratively little change in the lateral lobe. The number of teeth 

 along the end has increased, and two rudimentary setae have ap- 

 peared just below the movable hook. These setse are exceedingly 

 interesting from an historical standpoint, as raptorial setse never 

 appear upon the later nymphal or upon the adult labia of Anax 

 Junius, and were believed never to be present in the family. In 

 contrast to the lateral lobe, the ligula has developed enormously, 

 having almost the appearance which it exhibits in a full grown 

 nymph, with the exception of a group of four teeth on either side of 

 the cleft. The suture beneath the .l)order of the ligula, which was 

 noted in Lestes uncata, appears here also. In the next succeeding 

 stage (Plate IV, Fig. 4) we have a slightly later stage of develop- 

 ment. The differences are, however, slight, consisting in the appear- 

 ance of a number of teetii on the inner edge on the end hook and 

 of a second group upon the border of the ligula. 



The development of the labium of Basiceschna janata is along 

 much the same lines as that of Anax. In the condition shown in 

 PI. IV, Fig. 5, we have a state strictly comparable to that shown in 

 Fig. 4 of the same plate. In this figure one of the teeth upon the 

 end is already slightly separated from the others and has become 

 longer. It is this tooth which remains as the end hook while the 

 others disappear. In a later stage (PI IV, Fig. 6) teeth have 

 appeared upon the inner edge of the lateral lobe and hairs are 

 doveloped along the edge of the ligula. In the next stage (PI. IV, 

 Fig. 7 ) the only difference is the decrease in size of the teeth on the 

 end of the lateral lobe and on either side of the cleft in the ligula, 

 and in the almost complete closure of that cleft. In the last stage 

 Plate IV, Fig. 8) the end hook has become more hook-like. The 

 one tooth has l)ecome a hook itself, and the others are represented 



