1919] Welch: Pyrausta Penitalis 219 



leaf showing evidence of it, and occasional leaves are affected 

 only in this way. Sometimes, the entire margin is turned lip 

 and tied over. Funnels formed in this fashion are effective 

 retreats and provide efficiently against the larvae being washed 

 away by wave-action. Sometimes, the turned over edge collects 

 a small quantity of water, and the larvae may be partly sub- 

 merged for a time, although no inconvenience seems to be 

 suffered. Since complete filling of the peripheral tunnels with 

 water is possible, the larvae may, in such an emergency, escape 

 drowning by migration to the petiole junction — a region more 

 elevated, normally, than the margins and more likely to be free 

 from water. The rare occurrence of pupa; in these upturned 

 margins will be mentioned later. Whether the leaf-feeding 

 period is confined to certain instars was not determined. 

 Exuviae from small larvae were frequently seen, particularly 

 under the webbings. Field observations on hundreds of larvae 

 showed that the surface feeders include individuals up to about 

 14 mm. in length. It thus appears that more than one instar 

 are included in this period. 



Petiole Period. — When a certain growth is attained (appar- 

 ently about 14 mm.), a distinct change in the feeding habit 

 occurs. Surface feeding under webbings is abandoned and the 

 larva begins to tunnel lengthwise into the upper end of the 

 petiole, boring through from the upper surface. By what 

 means the petiole-leaf junction is located with striking exactness 

 is a matter of conjecture. Instances were observed in which 

 wandering larvae encountered an uninfested leaf, located 

 immediately the petiole junction and began excavation. Some- 

 times, the larva bores into one of the chief veins of the leaf, 

 tunneling down it to the petiole. Occasional failure to make 

 exact connection with the end of the petiole, resulting merely 

 in a hole through the leaf, is compensated for by constructing 

 an entrance into the side of the petiole just beneath the leaf. 

 A surface net is often constructed over the petiole-leaf junction 

 beneath which the larva works in forming the burrow. When 

 disturbed, it ma}' leave this shelter, wander about over the 

 leaf for a time, later returning to the web or seeking refuge 

 under old nets at the periphery. 



The burrow varies somewhat but usually the length is about 

 23-70 mm. and the diameter a little greater than that of the 

 larva itself. Its entrance is often surrounded by an accumula- 



