1!V l;. .7. TIIJ.YAKD. 67 3 



more larvceof S. enstalacta Tliese latter were placed in a separate 

 aquariuD). Three of them attempted to swim downwards, but 

 could not, as their bodies were so light. They then took up a 

 position similar to that adopted by Notonecta, walking under the 

 surface of the water, with legs uppermost. In this position they 

 caught and ate a fair number of mosquito-larvje. A few hours 

 later they managed to swim to the bottom. It was ludicrous to 

 see their attempts at covering themselves with sand. No sooner 

 had they heaped a fair quantity on to their backs, and striven to 

 settle down flat in it, than the buoyancy of their bodies overcame 

 them, and they rose helplessly up into the water. To-day, a 

 fortnight later, only one has so far succeeded in burj'ing itself. 

 Tlie other two sit on the lead at the corner of the aquarium ami 

 feed quite contentedly. 



Finally, the fourth larva floated, to all appearance dead, for six 

 hours. It then showed signs of life, and adopted the Notonecta 

 attitude. It remained thus for Ave or six days, feeding well. It 

 is now able to crawl about in the water-weed, but is still too 

 buoyant to keep on the sandy bottom. 



Of the eight larvae I now possess, which have passed through 

 this trying ordeal, I trust that some will emerge next summer. 

 It will be most interesting to see the effect of their experiences 

 on the size and colour-pattern of the resulting imagines. 



I should like to add that I was most careful to test the dry- 

 ness of the Srind, helow the surface, by digging; and satisfied 

 myself that on February 16th the sand was ahsoliUely dry and 

 caked hard throughout, right down to the bottom of the tank. 

 (The total depth of sand was only three inches). 



The chief conclusion to be drawn from this experiment is that 

 the larva of Synthemis eustalacta possesses the power of resisting 

 drought to a most remarkable degree. This is all the more 

 surprising, inasmuch as none of the species of this genus are 

 found in the drier parts of Australia. On the Blue Mountains, 

 where I obtained the larvte, the average rainfall is very heavy, 

 ranging from 30 to over 50 inches per annum. Droughts, how- 

 ever, of some duration are known to occur. The test that I 

 51 



