346 MONOGRAPH OF THE GENUS SYNTHEMIS, 



Hab. — Northei n Tasmania. I took it at St. Patrick's River, 

 Launceston, and Cressy, in December, 1908, and January, 1909. 

 I did not find it in Southern Tasmania. 



Tlie type-series was taken along the swiftly-running mountain- 

 stream, where, no doubt, the larvae lived. At Launceston and 

 Cressy the insects were found inhabiting swamps — localities 

 similar to those frequented by S. eustalacta on the mainland. 



This species is the Tasmanian representative of *S'. eustalacta, 

 the latter not being found in the island. Differentiation from 

 the parent-stock has proceeded far enough, in my opinion, to 

 justify the separation of the island-form as a separate species. 

 Apart from its very much smaller size and duller colouration — ■ 

 characters which in themselves make the two species easily dis- 

 tinguished at a glance, though of little morphological value — 

 there is a constant difference in the appendages of both sexes. 

 In S. eustalacta ^, the inferior appendage is just about two- 

 thirds as long as the superior; that of S. tasmanica ^, is larger 

 by comparison, and somewhat more truncate. In «S'. etostalacta <^, 

 the appendages are more leaf-like and less cylindrical than in S. 

 tasmanica 5; also the ovipositor of the latter is shorter and more 

 upcurved tlian that of the former; these differences are clearly 

 shewn in the diagrams of Plate vii. (compare figs.l and 2, and 

 figs. 19 and 20). 



The colour-scheme of the St. Patrick's series, when alive, was 

 rich chocolate-brown with pale yellow spots. So different were 

 they from all S. eustalacta I had ever taken, that 1 never connected 

 the two species until, on examination, I found the depressed 

 dorsal spine on segment 10 of the male. Later, when I took 

 specimens flying on swamps at Launceston and Cressy, I noticed 

 that these had more the colouring of typical S. eustalacta. It 

 seems, therefore, that the duller colouration is brought about by 

 a change of living, from stagnant to running water. This is also 

 the case with other members of the group; the brilliantly coloured 

 S. macrostigma, S. regina and aS*. eustalacta are dwellers in slow 

 or stagnant water, while the duller 8. leachii and the darkly 

 coloured Metatheuiis subgroup live in running streams. 



