Larvae and their Work 



The female flits along the surface of running streams and 

 lays her eggs on rocks just below the water. Running, 

 pure water is as necessary to this insect as was stagnant 

 water to the "drone-fly" larva. In due course the larvae 

 emerge, and they spend their lives standing on their tails 

 or crawling from place to place with a curious looping 

 action, like a leech or a looper caterpillar. 



Now, dwelling in running water and being quite unable 

 to swim, there is always a danger of these little creatures 

 being washed down-stream. True, they are armed with 

 hooks on their sucker feet which enable them to obtain 

 a firm hold of slippery rocks. In addition to these hooks, 

 they spin fine life-lines. When alarmed they leave go of 

 their resting-places and swing out on the end of their 

 silken life-lines, hauling themselves back to rest when 

 danger no longer threatens. When fully fed, they make 

 slipper-shaped nests, not unlike those of swallows, and 

 these they glue to a water weed with the open ends 

 pointing up-stream. 



At first the nests are closed, but later the broad ends 

 are removed. In these nests they turn into pupae, and 

 when ready to emerge as flies a wonderful thing happens. 

 The adult is a gauzy-winged creature which could not 

 stand immersion in water, yet it emerges below water and 

 in this manner. The pupae take up air from their sur- 

 roundings, and as a consequence a bubble of air collects 

 between the slipper-shaped nest and the pupae. When the 

 fly emerges, it does so in a bubble of air. Fly and bubble 

 rise to the surface and the insect goes on its way with 

 wings unscathed. Could anything be more marvellous ? 



