302 ON" DIMORPHISM IN THE FEMALE OF ISCHXURA HETEROSTICTA, BURM. By R. J. TiLLYARD, B.A. The pretty little dragonfly, Iscluiura heterosticta, belongs to the family Agrionidce, of which there are about thirty known species in Australia. Of these, six belong to the genus Ischnura. They are remarkable for their brilliant colours and small size. Very little is known of their habits, owing to the difficulty of collect-ing them. /. heterosticta is our largest species; the male, being very conspicuous, is often collected where the duller female is overlooked. It is common in the neighbourhood of Sydney, and extends southwards across Victoria to South Australia, while northwards it is plentiful as far as Brisbane, and probably has an extended range further up the coast. It flies from October to March. While collecting at Cook's River in February last, I found a remarkable new female form of this species. An hour's hunting had yielded about a dozen beautifully coloured insects which appeared to be males, with half a dozen females of the ordinary dull blackish type. On examination, however, it was found that^ with the exception of three, all the supposed males were in reality females; yet so closely did they resemble the male in form and colouring that the fact might easily have been overlooked. The male differs from the typical female in having the sides of the thorax, the first two and last two segments of the abdomen brilliantly coloured with rich blue. The female has no blue markings, and the abdomen is of a uniform dull fuscous, approach-ing black. The abdomen of the male is very slender, with the
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