1919] Welch: Pyrausta Penitalis 225 



tunnel. Whether the tissues of the pupa were actually used as 

 food or whether the tunnel making instinct of the invading larva 

 caused it to excavate anything which obstructed passage was 

 not determined. 



SUMMARY. 



1. Pyrausta penitalis Grt. (Pyralidas) occurs abundantly in 

 certain protected situations about Lake Erie in connection with 

 its favorite food plant, Nelumbo lutea. It belongs to that 

 extremely limited but interesting, heterogeneous group of 

 Lepidoptera, which has made progress in the development of 

 aquatic adjustments. 



2. The life-cycle is imperfectly known. Evidence indicates 

 at least two generations per year. Larvas and pupae develop in 

 connection with Nelumbo, and eggs, described for the first time, 

 occur on the same plant. Previous writers report relations not 

 only to certain other aquatic plants, but also to two strictly 

 terrestrial ones. Dependable data on the hibernation are lacking. 



3. While successfully adjusted to aquatic surroundings, 

 this species has retained the ability to utilize terrestrial con- 

 ditions, at least to a limited extent. The complete, original, 

 terrestrial organization has apparently been retained also, so 

 that the aquatic adaptations manifested are very largely, if not 

 exclusively, physiological. 



4. Surface feeding by young larvae occurs under silken 

 webs so constructed as to afford adequate protection against 

 dislodgment by wave-action, an ever present menace. The 

 upturned, silk bound margins of the leaf function similarly. 

 Older larvas construct short petiole tunnels which function 

 only as places for retreat and protection, from which a different 

 type of surface feeding is performed. 



5. The older larvae possess a well-developed, efficient form 

 of surface swimming consisting of an alternate, horizontal, 

 whip-like motion of the posterior portion of the body. They 

 have, however, no ability to swim under the surface and, when 

 completely submerged, sink to the bottom. 



G. While an older larva can withstand constant submergence 

 for about one and one-half hours, its typical holopneustic 

 tracheation necessitates access to the atmosphere. Protection 

 from prolonged submergence is provided in part by the water- 



