FIELD BOOK OF PONDS AND STREAMS 



the great group of North American moths and butterflies only * 

 a few moths, most of them belonging to one family, the 

 Subfamily NymphulincE, have aquatic larvas. They are 

 typical caterpillars which have six true jointed legs on the 

 thorax, and flesh}^ prolegs on the abdomen. 



They feed upon diatoms and the tissues of higher plants. 

 Most of them live in quiet waters overgrown with bladder- j 

 worts, Elodea, pickerel- weed, or the yellow and white pond- 

 lilies. At least one species has been found in swift streams. 



About half of them breathe air, the others breathe through 

 thread-like gills which are arranged in rows along the sides 

 of the body. Those of the genus Nymphula bite o^ pieces 

 of leaf and make cases which they line with silk. 



^f^^ 





Fig. 200. — i, Lily -leaf caterpillar, Nymphula ma^ 

 culalis, and 2, its floating leaf -case; 3, the moth 

 (one inch long). 



Lily-leaf caterpillar, Nymphula maculalis. — The cater- 

 pillars of Nymphula maciilalis, the lily-leaf caterpillar (Fig. 

 200), are common in quiet water among yellow and white 

 water-lilies. They live in leaf-cases (Fig. 200) which they 

 make by biting off two pieces of lily pad, each about an inch 

 long, and fastening the edges together with strands of silk, 

 or sometimes they bite off one section and attach it to the 

 underside of the same lily pad. The pieces are arranged 

 shiny side out and almost always appear newly cut. Some- 



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