AQUATIC INSECTS 



liiy, water-plantain, and Potamogetons, and all have a similar 

 life-histor\\ Only the adults and eggs are easily found. 

 Their entire life cycle is still another example of the way in 

 which insects though living several feet under water still 

 contrive to breathe air. 



Fig. 2 1 6. — Leaf -beetle, Donacia palmata, laying 

 her eggs on the underside of a lily pad through a 

 hole which she has cut. Length of adult, one half 

 inch. 



The long-homed leaf-beetles of the genus Donacia can be 

 seen about ponds on any bright summer da}^ walking over 

 the lily pads, flying up into the air and returning again to the 

 lilies. They gleam in the sunshine with metallic green, or 

 bronze, or purple against the dark lily leaves. The under 

 sides of their bodies are pale brownish, and clothed with silky 

 hairs which keep them from getting wet. They hold their 

 long antennae arched downward in front of them, busily feel- 

 ing the leaf surfaces wherever they walk over them. 



In ponds where these beetles are abundant the lily pads 

 are riddled with holes where they have laid eggs (Fig. 216). 

 When a female is ready to lay her eggs she stands on the upper 

 surface of the leaf, bites a hole in it about one-quarter of an 

 inch in diameter, inserts her abdomen through the hole and 

 lays her eggs in a circle, often an incomplete one, on the under 

 side, placing a double row of eggs in each circle and fasten- 

 ing them to the leaf by a gelatinous glue (Fig. 217). These 



279 



