194 INSECT ARTIZANS AND THEIR WORK 



to the leaf or to a twig that will enable it to reach 

 the leaf. 



If in summer time we visit any considerable 

 pond where there are plenty of water-weeds, we 

 are sure to be attracted by the sight of numerous 

 pretty moths flying about over the water and 

 settling on the aquatic vegetation. These represent 

 several species of Pyrales, and are popularly known 

 as China-marks from the character of their wing 

 ornamentation. The reason for their presence in 

 this rather unlikely habitat for day-flying moths 

 is that their caterpillars are aquatic, which in itself 

 is an unusual thing for the caterpillar of a moth. 



The caterpillar of the Brown China- mark (Hydro- 

 campa nympbeata) feeds upon the leaves of the 

 Broad-leaved Pond- weed (Potamogeton natans), whose 

 brownish, oily-looking ovals float with the lower 

 surface in close contact with the water and the 

 upper surface exposed to the air and always dry. 

 Now' the caterpillar might feed on the upper surface 

 of the leaves and, so long as it did not eat through 

 the lower cuticle, run little risk of being drowned. 

 But this the species has probably found out in 

 the far past would expose it to the attacks of many 

 enemies. So it has chosen to spend its existence 

 as a caterpillar on the under side of the leaf, though 

 this necessitates always being submerged. 



But our caterpillar is one of the tailors, though 

 not one of the common run. Long before man 

 ever thought of descending into deep water dressed 

 in a watertight costume that contained air, our 



