BY R. J. TILLYARD. 



411 



abundance around isolated water-holes of stagnant water, these 

 being its favourite haunts. Next in point of favour come the 

 swamps, where in company with Diplacodes bipunctata it is often 

 found in profusion. It also inhabits slowly running streams, 

 but not so abundantly, the larva? only congregating in certain 

 suitable spots, and probably often suffering destruction from 

 freshets, and also from small fishes and other aquatic creatures. 



Time of Appearance — It is probable that this species 

 is double-brooded; though I have only reared the spring brood, 

 which is more abundant. As is usual with the Odonata, the 

 females appear before the males. The latter are found through- 

 out the summer more abundantly than the females in a propor- 

 tion of about 2 to 1, and at the end of autumn are still more 

 proportionately abundant. The following dates of the first and 

 last emergences of the imago from my aquarium are of interest : — 



Date. 



First emergence. 



Last emergence. 



$ 



9 



s 



9 



1904 



Aug. 27th 



Aug. 8th 



Sept. 7 th 



Sept. 7th 



1905 



Sept. 21st 



Sept. 3rd 



Oct. 9th 



Oct. 4th 



To account for the difference in the dates of appearance in 

 1904 and 1905, it must be remembered that in the latter year 

 June and July were exceedingly dry months, nearly all the 

 water-holes around Sydney being dried up, thus retarding the 

 growth of the larvse. Moreover in August and September the 

 cold weather continued much longer than in 1904, so that the 

 above result was only to be expected. 



Throughout September and October the spring brood appears 

 in great numbers around Sydney ; and the perfect insect swarms 

 on all the creeks and water-holes right up to December. There 

 then appears to be a decided falling off in numbers. Probably 



