1916] Biology of Aquatic Lepidoptera 185 



6. Tracheal gills first appear in the second instar. Paired, 

 lateral, filamentous gills occur on all of the segments except the 

 prothorax and the last abdominal. Maximum number of gills 

 per segment is two. 



7. In the third instar, an increase in the number of gills 

 appears, the maximum number being three. Dorsal, paired, 

 filamentous gills also appear. 



8. The sole method of locomotion by larvae is an inefficient 

 crawHng. There is no evidence of an abiHty to swim. When 

 supported by a case, change of position can be effected by side 

 to side motions of a portion of the body extended into the water. 



9. Case-making is a constant larval activity from time of 

 hatching to pupation and sometimes seriously reduces the leaf 

 surface of the food plants. The chief functions of the case 

 seem to be (1) protection, and (2) support in the water. 



10. No evidence of feeding or case construction which 

 involved plants other than Nymphcea americana was observed, 

 although the larva has been reported in connection with 

 Castalia and Brasenia. 



11. After the first instar, tracheal gills constitute the 

 larval respiratory organs. The maximum number of gills 

 increases with advancing age from two per segment in the 

 second instar to as many as ten per segment in the mature larva. 

 The total number of gills increases from twenty-two in the 

 second instar to one hundred in the mature larva. The number 

 of gill filaments per segment increases from four in the second 

 instar to as high as forty-eight in the full-grown larva. The 

 total number of gill filaments on the body of a larva increases 

 from forty in the second instar to over four hundred in the full- 

 grown larva. 



12. Dissemination in the larval stage is accompHshed by 

 crawling over contiguous leaves; by voluntary propulsion in 

 detached cases ; by the effects of winds, waves, and currents on 

 detached cases; and indirectly by the work of certain other 

 insects which cause a separation of the leaves of the food plant 

 from the petiole. 



13. The pupa is described in detail. It is usually attached 

 to the lower, submerged surface of the water-lily leaf and is 

 enclosed in a silken covering which, in turn, is surrounded by 

 the last larval case. 



