lO Searle, The Pond and its Inhahitavis. [yj' 



ict. Nat. 

 XXXIV. 



other side of the world. A number of aquatic animals produce 

 resting eg^'>, or have resting stages, wherein they retain their 

 vitality for lengthy periods, and this explains why pools that 

 have been dry for a considerable time, on again being filled 

 with water are soon swarming with animal life. 



There are a great many species of Cladocera in the pools 

 around Melbourne, and all are objects of extreme interest. 

 Some, like Daphnia, are found in open water ; these belong to 

 the genera Ceriodaphnia, Moina, Pseudomoina. Bosmina, &c. 

 Others are found amongst the water weeds ; these are Simo- 

 cephalus, Chydorus, Alona, &c., and all are parthenogenetic. 



The Whirligig Beetles — GYRiNiDiE. 



Anyone who has visited a pond or a quiet nook on a stream 

 must have seen the Whirligig Beetles engaged in their amazing 

 dances, making all manner of curves and crossing each other's 

 course without ever a collision, rushing madly in and out in a 

 very frenzy of excited movement, full of complexity and grace. 

 But, make an attempt to sweep some of them into your net, 

 and they scatter in an instant, diving and swimming out of 

 reach of danger, assembling again when all is quiet to resume 

 their surprising evolutions. Members of this remarkable family 

 are found all over the world, from sea-level to snow-line, and all 

 indulge in these peculiar gyrations. 



A most remarkable feature in this beetle is its eyes. These 

 are large, and nearly spherical, but are each divided by a ridge 

 of chitinous material into two, so that the beetle appears to have 

 four eyes, an arrangement of great use to the insect, for, as it 

 swims about, two of the eyes are searching for food below the 

 water, while the other two keep a lookout above. Their food 

 consists of dead insects, which they find in the water, or 

 disabled ones that happen to fall on the surface of the pond. 



In leaving the pond for nocturnal flight, this beetle has to 

 climb out of the water up the stem of some plant a few inches 

 before it can use its wings. It flies with a rapid, whirring. flight, 

 and often to a great distance from water, as may be observed 

 from their presence around the electric light globes of the city. 

 Though such excellent swimmers and capable fliers, when they 

 come to earth they are anything but graceful insects. Their 

 first pair of legs are long, and are used for climbing out of the 

 water, while the other two pairs are very short, and while they 

 are admirably adapted for swimming, are not of great service 

 for walking on earth : their motion is a series of hops and 

 wriggles, and, unless they can climb to an elevation, they are not 

 able to again take to flight, so many perish by being crushed 

 under foot on the sidewalks. 



The female beetle Jays her eggs on the leaves of a water 

 plant ; they are placed end to end in parallel rows. The eggs 



