304: DIMORPHISM IN FEMALE OF ISCIiyUJiA IIETEROSTICTA 



Forma A. 

 Abdomen. — Shape stouter 

 than in ^, cylindrical. 



Colour dull black or fuscous; 

 in some specimens there is a 

 tinge of bronze, in others, pro- 

 bably the most mature, a slight 

 covering of powdery greyish 

 bloom. Segments 8 and 9 paler, 

 of a brownish-bronze. Under- 

 side greyish. 



FOKMA B. 



Abdomen. — Shape slightly 

 stouter than in (J, but not so 

 stout as in A; the first two 

 segments very slightly enlarged; 

 segments 8 and 9 also some- 

 what enlarged, as in $. 



Colour. — Segment 1 blue; 2 

 blue with a dorsal spot of deep 

 bionze in the form of an up- 

 turned goblet; in some speci- 

 mens this s|)ot exten'ls over the 

 whole dorsal surface of 2; 3-7 

 deep bronze; 8 bright blue; 9 

 bright blue, with a deep trans- 

 verse black band in the suture; 

 10 black. Underside dull 

 greyish. 

 Appendages very small, rather Appendages as in A. 



blunt, separated, black. 



Forma B of the 9 differs from the male as follows : — 

 The transverse epicranial band of bluish-green in Forma B is 

 replaced by one of brilliant blue in the $. Abdomen more 

 cylindrical, slightly stouter than in $. The appendages of 

 course differ as usual in the sexes. In the wings the only 

 difiference is a generic characteristic, viz., tlie pterostigma of the 

 forewings of the ^ is black, while in both forms of the 9 it is 

 olive-brown. 



It is difficult to account for the existence of Form B. We 

 know that the genus Ischnura exhibits in some of its species a 

 variation of colouring in the 9, for an American species* has 

 been described having a typical green 9 and an orange form also. 

 This, however, appears to be merely a variety in which the 



Kellicott, " Dragonfiies of Ohio," p. 48, Ischnura vertical^, Say. 



