1922.] lunula of the Chilka Lake : Observations in Rambha Bay. 697 



able that the amphibious and littoral forms seem to have been affected more than 

 any others. It is also interesting to note that none of the pelagic species (except 

 those only found previously when the water was at its saltest) have apparently 

 diminished in numbers, though one of the most abundant (Lucifer hanseni) belongs 

 to a marine genus. I have been able to obtain no evidence of any fresh invasion of 

 lacustrine or fluviatile species to take the place of those that have died out. 



Insecta. 



Ephemer opter a. — A swarm of large may-flies was observed on the surface of the 

 lake off Barkuda on Sept. 23, 1920. They were, however, fully mature and may have 

 emerged from some body of fresh water in the neighbourhood and have been blown 

 out on to the lake. They were evidently in a moribund condition. No members of 

 this order were observed in the bay in 1914. 



Odonata. — The dragon-fly Pseudagrion microccphalum (Ramb.) was as common 

 in 1919-20 in Rambha Bay as it was in all parts of the lake in 1914. It was 

 observed to breed in the lake in preference to the pond 011 Barkuda. The imago is 

 common at all seasons, but particularly so at the beginning of the rains. The nymph 

 emerges in the evening, as a rule on masses of dead weed on the shore, a ad there 

 undergoes its final metamorphosis. Numbers of teneral adults, only able to flutter, 

 can often be seen in the early morning at the edge of the water. Anax guttatus 

 (Burm.) also breeds in the lake and probably Brachythemis contaminata Brauer, which 

 skims along the shore in the evening, catching the sandhoppers (Orchestia platensis) 

 as they leap into the air. 



Rhynchota. — E urates formidabilis Distant, was just as common on the surface 

 of the bay in 1920 as it was in 1914. A single winged specimen of Gerris spinolae was 

 observed from the landing-stage at Barkuda on the first day of the rains, June nth. 

 It was first noticed on a stone at the margin and may have just alighted from flight. 



Diptera. — Anopheles rossii Giles, as in 1914, was the only mosquito found breed- 

 ing in the lake in 1919-20. Imagines were enormously abundant on Barkuda, ap- 

 parently coming from the lake, in the latter part of the rains of 191 9 and the hot 

 weather of 1920. Fortunately they are very easily affected by movements of the 

 air and do not become really active till fairly late in the evening. In the day-time 

 they hide in hollow trees, in crannies among the rocks and in corners of badly- ven- 

 tilated rooms. 



Moixusca. \ 



Twenty species of living Mollusca were taken in Rambha Bay in 1914, 12 species 

 belonging to the Gastropoda and 8 to the Pelecypoda. Among the gastropods no 

 less than 8 families are represented, and among the bivalves 6 families. Of the 20 

 families only one (the Hydrobiidae) is not essentially marine, and Stenothyra, the 

 genus present, is essentially estuarine. The Mollusca, therefore, afford particularly 

 good material for estimating the results of changes in salinity of the water of the 

 Chilka I^ake on the fauna, the more so as many of the species were extremely abun- 

 dant in 1914 and are easily recognized. 



