196 INSECT ARTIZANS AND THEIR WORK 



when the head of the insect is withdrawn the lips 

 of the opening press together as though closed by a 

 spring. 



A remarkable feature of the story is the fact that 

 when the caterpillar emerges from the egg it is a 

 purely aquatic insect, breathing through its skin 

 the oxygen that is dissolved in the water, for its 

 system of air tubes is not developed and their 

 external openings are closed. At this period, too, 

 it is a miner in the leaves of Potamogeton, and its 

 mines are full of water. Its skin is smooth and 

 remains wetted. Its mining life only lasts a few 

 days ; then it becomes a tailor, fashioning a suit 

 of clothes that is only a protection from enemies. 



It was born in July or August, and like other 

 larvae it casts its skin several times to allow increase 

 of size, but no striking change takes place in its 

 structure or habits until the following May. Then 

 it constructs its waterproof suit of clothes. Then 

 its new skin is studded all over with conical points, 

 large and small, which serve to keep air entangled 

 between them, so that if you take it out of its case 

 and drop it in the water it will not become wetted. 

 The spiracles along its sides open to admit atmos- 

 pheric air to its fully developed system of air-tubes 

 {trachece), and its new case remains always filled 

 with air. In June or July — after a short period 

 of rest as a chrysalis— it emerges as a beautiful 

 moth, which i^ies among the reeds. 



Very similar is the story of the Small China-mark 

 {Cataclysta lemnata) which begins life as an aquatic 



