100 LIFE STORIES OF AUSTRALIAN INSECTS. 



firmly secured to the rock which serves as 

 shelter for the larva of this genus. The active^ 

 larva of the mayfly Atalophlebia proved most in- 

 teresting- when examined w^ith a lens in a brighl 

 light, the rapid rhythmic motion of its gills being] 

 specially fascinating. Several interesting dragon 

 fly larvae were collected, including Austrocordulia 

 refracta, Acschna brevistyla, Hemigomphus hetero- 

 clitus; the latter were obtained by careful 

 searching of the clean sand of the creek bed, whilst 

 the Aeschna larvae were best obtained by dredging 

 the vegetable debris. 



The larger dragon-fly larvae were put into a dish 

 with a little fine mud amongst the water. This 

 served to detect the current of water which is 

 ejected from the rectum with sufficient momentum 

 to cause the forward propulsion of the larvae. In 

 such cases the gills are internal, and line the walls, 

 of the rectum; they absorb the oxygen from thej 

 \Vater before it is ejected. The more rapid the 

 swimming movement the more abundant is the sup- 

 ply of oxygen for respiration. This method oi] 

 propulsion was actually tried on an experimental 

 scale for the propelling of boats, but proved inferior, 

 to the screw. 



It is worth notice that in many cases the dragon- 

 fly larvae were in various stages of development. 

 Thus by patient search, it Avas possible to see a 

 considerable portion of the life-history without the 

 long waiting so often necessary in the case of cer- 

 tain other genera where the individuals are all at 

 the same age at a given time." 



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