IV AQUATIC CATERPILLARS 229 



close-woven silk.^ The pupa resembles that of a small 

 terrestrial Moth. It breathes by three pairs of well- 

 developed spiracles, carried on prominent warts which 

 stand out from the sides of the thorax. There 

 is a short ventral projection of unknown use. The 

 emergence of the Moth has not been described. 



Reaumur discovered the eggs of the Moth, which 

 are laid on the under side' of the leaves, near the 

 edge, and enclosed, as is so often the case with 

 aquatic Insects, in a transparent jelly. From forty 

 to one hundred eggs are arranged with great regu- 

 larity in one patch, and according to Reaumur, the 

 female Moth protects the mass by glueing a piece 

 of leaf over the whole. -^ The larvae hatch out in July 

 or August, and at once begin to make their own 

 sheaths. 



Mijller has added some interesting facts to 

 Reaumur's account.-^ He tells us that the young 

 larva, which is about r8 mm. long, is completely 

 wetted with water. Its spiracles are rudimentary, 

 and do not communicate with special air-tubes. 

 The surface of the body has at first no pointed 

 prominences, such as those which at a later time 

 prevent the skin from being wetted. It must depend 

 for its supply of air upon the oxygen dissolved in 

 the water, though it has no gills or branchial organs 

 of any kind. The sheath which it makes for its own 



' Reaumur says that the cocoon is attached to a submerged 

 leaf, but this does not agree with what I have observed. 



- I have found the eggs completely exposed. 



^ " Beob. an im Wasser lebenden Schmetterlingsraupen," 

 von G. W. MuUer, Zool. Jahrb. VI. p. 617. 



