THE BroLtocy oF EKPHYDRA SUBOPACA LOEW 595 
weather prevails, the water in the overflowed areas is rapidly diminished 
by evaporation and a great number of larvae are left on land. They 
sluggishly but steadily crawl about, seeking recesses in the soft mud. 
They come to some rocks, pebbles, sticks of wood, and the like, that 
are scattered here and there over the areas, and hide underneath. 
_ Large numbers of larvae stay quite away from the shore, in the deeper 
water, and retreat with the receding water into deeper parts until 
finally the water is all gone; then they embed themselves in the soft mud 
and their dorsa are covered with dirt and scums. Such a covering is a 
great protection to the life of the larvae in dry weather. Two or three 
days after the water had receded, a larva was picked up from the mud 
or from the underside of a log or a rock and placed in water. It was found 
alive, crawling and wriggling as usual. 
In midsummer, showers or gentle rains frequently flood the temporarily 
dried areas and the bottom mud becomes soft. Both the hidden and 
the embedded larvae begin to crawl, often producing long trails on the 
surface of the mud by the scratching of the last pair of prolegs of each larva. 
These trails are numerous, and are arranged irregularly and often of 
considerable length. They look like the prints made by pressing a bunch 
of twisted threads on the mud. In the laboratory some mud brought 
from the salt pools was entirely drained of water and a number of 
larvae were placed in it. They behaved just as those had done 
outdoors — that is, hiding themselves under pebbles and embedding 
themselves in the mud. Afterward, laryae picked up from the mud and 
placed in water were always found to be alive. At the end of the fifth 
day, they were found dead in the thoroughly dried mud. With such 
ability for resisting desiccation, the larva has much chance to get through 
a drought that does not last very long. The mud in the overflowed areas 
is always moistened by dews at night, and as long as moisture is present 
in the mud the larva will be able to live. Consequently, throughout the 
season very few larvae have been found killed by drought. 
Gravity.— In summer and fall, when the larvae are active in swimming and 
feeding, they often float up to the surface and stay there for some time. 
They rise easily, but go to the bottom only with considerable effort. 
In the laboratory, when a grown larva is transferred from one aquarium 
to another it seldom goes to the bottom; it is often buoyed up again 
after it has been forced down. 
