BY R. .1. TILLYARD. 593 



These epicranial patterns are, uf course, subject to slight indi- 

 vidual variation, but are sufficiently constant to be relied upon. 



(2). D. lestdides $ can be recognised at once by the great length 

 of its fore-legs. The measurements for the tibiae are — D. lestdides 

 9 7; Z). euphvudides 9 4-5; D. nymphdidcs 9 5 mm. 



(3). The measurements for the hindwing are-Z>. lestdides <^ 

 34-35 long, greatest breadth 6; D. euphvedides $ 32 by 6; D. 

 nijmphdides 32 by 6'2mm. 



(4;. In comparing the abdomens of the three females, that of D. 

 lestdides is seen to be very cylindrical, somewhat flattened, and 

 much broader than either of the others; that of D. euphvedides is 

 distinctly narrow and rounded; while that of D. nymphdides is of 

 intermediate breadth and roundness. 



Besides these differences, it may be remarked that the ptero- 

 stigma of D. euphcedides is narrower and slightly shorter than 

 those of the other two. In the whole of my series of B. nym- 

 phdides 2, the pterostigmas are uniformly pale cream-colour 

 between black nervures; those of D. lestdides 9 are usually so, and 

 those of D. pAipJumdides much darker. These differences, however, 

 cannot be pressed, as we do not know what changes may take 

 place in the colouration as the insects become more and more 

 mature. 



Life- Histories of D. lestdides Selys., and D. nymphdides, n.sp. 



In my former paper on the life-history of D. lestdides,* I was 

 compelled to leave some una\oidable gaps in the record, as I had 

 been unable to find tlie full-fed nymph, and could only surmise 

 what its habits might be. The beds of the mountain-creeks of 

 the Rodriguez Pass and other parts of the Blue Mountains, and 

 also the Heathcote Creek and Woronora River in the Illawarra 

 district, (the places where I studied this species) are remarkable 

 in consisting almost entirely of .solid bed-rock. The detached 

 rocks and boulders are mostly of great size, and quite immovable. 

 There were none of the flat or rounded rocks of medium size that 

 so often occur in rapid streams. I made it my object to search 



"These Proceedings, 1909, xxxiv., p. 370. 



