584. Curn PING 
means of the last pair of prolegs, or with the prolegs of one on another 
part of the other, entangled and struggling aimlessly. 
Floating.— The larva often floats itself up to the surface. The larva 
does not necessarily touch the surface, but often stays about an inch 
below. Usually, when floating, the larva has its head pointing obliquely 
upward and its body held, bending or straight, in a somewhat horizontal 
position. However, there is no definite rule as to its position. 
Dropping.— Dropping may take place after wriggling, after staying 
below the surface for a considerable time, or immediately after floating. 
Sometimes the larva, instead of holding its head obliquely upward as it 
often does, reverses the process in making its way downward. In pools 
I and II, where the water is clear, this mode of locomotion can be best 
observed when the larva is getting near the bottom. Its body seldom 
touches the bottom, for at some point within an inch from the ground 
the larva will stop dropping and remain stationary. Sometimes wriggling 
may be assumed at this moment. Likewise, wriggling may also break 
in midway in dropping, so this mode of locomotion is likely to be inter- 
rupted almost anywhere before the end of the descent is approached 
Feeding 
Method of feeding— The larva often crawls on the surface of float- 
ing leaves and stops there to feed. Its mandibular sclerites move 
rapidly, bending back and forth. The head segment is extended and 
moves with frequency, corresponding to the movement of the cephalo- 
pharyngeal skeleton. The mouth parts graze vigorously on the materials 
deposited on the plant surface, and the tooth-like structures on the ventral 
side of the distal part of the mandibular sclerites comb up the desirable 
materials. As the larva seldom feeds long on one spot, its head swings 
freely in all directions seeking a new feeding place. While the larva is 
feeding at the surface of open water, the ventral side of the first segment, 
including the mouth, is flatly applied to the surface film. The continuity 
of the latter is frequently disturbed by the vibration of the oral lobes. 
These lobes with their chitinous tubercles serve as a sort of brush in pro- 
ducing little whirling currents, in which the microscopic organisms are 
involved and brought to the mouth. Meantime the inner, more prominent 
tubercles, which are situated close to the oral cavity, sweep simulta- 
neously toward the center. The mandibular and dental sclerites move 
forward to meet the flowing currents, and repeatedly relax and _ fall 
