452 ON THE GENUS NANNODYTHEM IS, 



9. Total length 24-26*5 mm.; abdomen 16-17-5 mm.; forewing 

 18-19*5 mm.; hindwing 17-18-5 mm. Wings as in male; bases 

 more suffused with saffron (2-3 mm.), pterostigma somewhat 

 larger. Head and thorax as in male. Abdomen broad, 

 subcylindrical, 2-3 slightly narrower than rest, 4-8 broadening, 

 narrower again. Colour : 1, black with basal and anal trans- 

 verse yellow lines. Rest of abdomen either fulvous, brown or 

 testaceous according to the individual and age; a more or less 

 irregular black dorsal line all the way down, swelling out at both 

 ends of each segment, very broad on 8-9. On each side an 

 irregular black sublateral band along 2, half of 3, and 4 6 or 7; 

 these two bands are connected with the dorsal band by transverse 

 black bands across the sutures, those of 2-3 narrow, the others 

 broader, and those of 7-9 separated by a fine orange linn along 

 the suture itself; 10, orange with a black basal spot. Underside 

 very flat, orange, with the ventral carina broadly black; broad 

 black bands across the sutures, carrying a pale spot on each side; 

 2-7 somewhat hairy beneath. Appendages 0'5 mm., wide 

 apart, straight, pointed, slightly hairy, orange with blackish tips; 

 separated by the tubercular projection of 10. 



Hob. — South- Western Australia : Wilgarrup, near Bridgetown. 

 Very rare. December-January. 



Habits similar to those of the preceding species. It occurs in 

 a tract of boggy country through which a small brook runs. It 

 is a stronger and probably more active species than the other 

 two, and has a zigzag and irregular flight. 



In order to grasp more fully the important differences between 

 these three closely allied species, I append a table of comparison 

 for the chief characters in which they differ, in neuration, size 

 and colouration. 



It seems fitting here to make a remark upon the group of 

 allied genera, placed by authors at the end of the Libellidinw, 

 which show an aberrancy in the formation of the triangle of one 

 or both wings. Too much stress has been laid upon the possession 

 of this remarkable property as regards its value in generic dis- 

 tinctions. There is no doubt of its importance, but there is also 



