170 Annals Entomological Society of America [Vol. IX, 



exhibited when larvae were submerged apart from a supporting 

 surface but such movements were ineffective so far as change of 

 position was concerned. However, another form of locomotion 

 will be described later in connection with the discussion of 

 case-making which serves as a substitute for true swimming. 



Case-making. — A very interesting phenomenon in connection 

 with the life history of N. maculalis is the case-making activities 

 of the larva. This habit is common to the genus Nymphida, 

 both in foreign and native species. Of the latter, Packard ('84, 

 p. 824) gave a brief account of case-making by what was 

 apparently N. icciusalis Wlk. Hart ('95, pp. 167-172, 176-180) 

 described it in N. (Paraponyx) obscuralis Grt. and N. {Hydro- 

 campa) obliteralis Wlk. Forbes ('10, pp. 220-21) gave a brief 

 description of case-making in N. maculalis Clem. 



The observations of the writer confirm, in most respects, 

 the brief description of Forbes on case-making in N. maculalis. 

 However, a number of additional data have been secured and 

 will be discussed in some detail. As mentioned above, the 

 larvas are active from the moment of hatching. They emerge 

 from the eggs and wander about restlessly for a time before 

 starting to feed. In some of the aquaria, this period of prelim- 

 inary wandering lasted for two or three hours. In the lab- 

 oratory, the young larv« seemed to show a preference for the 

 submerged lower side of the leaf on which they were reared. 

 The young larva, under laboratory conditions, soon began to 

 make an incision in the leaf which was extended in such a way 

 that ultimately a portion of the leaf, oval or circular in form 

 and about 2 mm. in maximum dimension, was cut out and 

 drawn back on the lower surface of the yellow water-Hly leaf so 

 that the larva was enclosed. Sometimes the larva cuts out the 

 upper surface of its compartment, thus making an independent 

 case composed of two similar pieces of leaf tied together by 

 silken threads. 



As the larva increases in size, the cases are outgrown and 

 new ones made. With the older larvae, case-making is a simple 

 and rather rapid process. In constructing a new case, the larva 

 crawls to the lower surface of a leaf and usually begins work 

 near the periphery so that the resulting piece is cut out of the 

 edge. However, an occasional leaf is found in which the piece 

 has been cut out near the midrib. Certain random, preHminary 



