1919] Welch: Pyrausta Penitalis 221 



bearing tissue and ultimately shows signs of deterioration. The 

 upper surface shows discoloration, loses its waterproof character, 

 and, in the Sandusky Bay region, usually becomes covered with 

 chironomid (Diptera) larvcC, which form their mud cases all 

 over the exposed surface. Burrow construction partly severs 

 the connection of the leaf with the rootstalk and often results 

 in the ultimate deterioration of the floating part, even in the 

 absence of surface feeding. Since the work of a single larva 

 may lead to leaf deterioration and since it is known that, when 

 present, the buds and seed-capsules are also attacked, it is 

 evident that P. penitalis is a serious enemy of Nelumbo. The 

 ability of the older larvae to migrate from leaf to leaf, as described 

 later, also increases their menace to the food-plant. 



LOCOMOTION. 



Crawling.^-Chsinge of position on the food-plant is accom- 

 plished by the ordinary methods of crawling. These larvae 

 are sufficiently active to enable them, where Nelumbo leaves are 

 contiguous, to wander widely from the hatching place. 



Swimming. — One of the noteworthy adjustments to the 

 aquatic surroundings appears in a well-developed form of 

 surface swimming. Larvae removed from petiole tunnels and 

 dropped lightly on the water remain supported on the surface. 

 After a few initial squirming movements, active swimming is 

 begun and, as long as nothing interferes with the surface position 

 of the larva, progression is distinctly efficient. Swimming 

 movements consist of an alternate, horizontal, whip-like 

 motion of the posterior half of the body. The sequence of 

 motions is as follows: The posterior end of the body is flexed 

 horizontally on one side into a position in which the caudal 

 end is directed cephalad; then, with a strong, quick sweep, as 

 if released from considerable lateral tension, it returns to the 

 normal position, stopping there for a brief interval; then 

 a similar flexure and return is made on the opposite side. 

 This whip-like motion, first on one side and then on the other, 

 resembles the action of a straight steel spring fixed at one end^ 

 bent laterally, suddenly released and stopped at the median 

 position without further vibration; then bent and released on 

 the opposite side. This strong, vigorous return of the posterior 

 end to its normal position constitutes an effective stroke against 

 the water and propels the animal at a goodly rate. So strong^ 



