BY R. J. TILLYARD. 739 



out the black centrally, leaving a more or less clepsydrate black 

 or bronze dorsal mark. The thoracic stripes are slightly different 

 in shape; the abdomen of L. io narrower but larger than that of 

 L. psyche. The females are exceedingly similar in shape and 

 markings, and are best separated by the shape of the wings, 

 which are narrower and much more pointed in L. io than in 

 L. psyche. 



24. ISCHNURA DELICATA Selys. 



Common in all marshy localities and on the lagoons, rarer on 

 the large mountain-streams. At Wilgarrup every patch of long 

 grass or sedge in the marshes yielded hundreds; and it was 

 a beautiful sight to see the swarms of males like brilliant red 

 needles tipped with blue, hovering over the grass after being 

 disturbed. This is one of the smallest known dragonflies, and 

 also one of the most beautiful, The abdomen of the male is very 

 slender, bright red tipped with light blue and a little black. 

 The ordinary female is either dull black or olive-green. At 

 Bridgetown and Wilgarrup I found a remarkable dimorphic 

 female, which imitates the colouring of the male. [See These 

 Proceedings, p. 190, " On Dimorphism in the Females of Austra- 

 lian Agrionid?e."] The proportion of dimorphs to ordinary 

 females was about 10%. This insect is abundant over the whole 

 of Australia, even in the dry central districts and in the tropics; 

 the northern forms are exceedingly smali. The dimorphic female 

 has not been found outside of Western Australia. 



24. PSEUDAGRION CCERULEU3I, n.sp. 



(Plate XXXV. figs. 13-14). 



(J. Total length 27 mm.; abdomen 22 mm.; forewing 145 mm., 

 hindwing 14 mm. 



Wings: Neuration slender, black. Pterostigma 06 mm., 

 black. Nodal Indicator 



behind. Ejjicranium 



2 7-9 Head: ^i/es dark blue, black 

 2 6-7i hairy, black, a brilliant blue 



wavy transverse band behind, reaching from eye to eye, and very 

 slightly enlarged at the ends; front ocellus transparent; two tiny 



