ey Annals Entomological Society of America [Vol. V, 
The nymphs have a wonderful clinging power. Their 
flattened bodies, and limbs which extend laterally, are pressed 
close to the rock, thus enabling the insects to retain their hold 
and escape the full force of the waves. The legs are supported 
distally with sharp claws which the nymph digs into the small 
holes and crevices of the stone. While removing the insects 
from the stones one can often feel the resistance which they offer 
despite their small size, and in some cases they cling with such 
force that their stubbornness often results in the loss of a limb 
or two. This misfortune however does not seem to be disas- 
trous to the vitality of the insect, and the lost appendages 
soon regenerate. ) 
Although the nymphs spend most of their time lying quietly, 
it is astonishing to see with what rapidity they can move with 
their flattened bodies over the moist surface of stones when 
they are disturbed, even if the stones are inverted so that the 
insect is compelled to move with its dorsal surface downward. 
The latter fashion appears to be even less difficult, owing 
probably to the fact that they almost continually cling to the 
under side of rocks in their natural habitat. They frequently 
move sidewise and even backward, and are so active that an 
attempt to collect them from stones under water is an almost 
impossible task. 
All summer these insects occupy a narrow strip, about three 
feet wide, along the lake shore and are particularly numerous 
on the shores of Picnic Point. Along in the latter part of 
October as the water turns cool, the nymphs slowly begin to 
migrate into deeper water and practically all desert the shallow 
water before the ice begins to form. A careful search was made 
on the day the ice broke up in the spring but not a single spect- 
men was seen. A few days after the ice disappears, however, 
the nymphs begin to make their appearance. 
I have never seen the nymphs swimming freely in their 
natural habitat, although when a stone to which several of 
them are attached is suddenly jerked out of the water, some 
become dislodged and quickly make for a neighboring rock. 
They swim in an undulating movement, bending the head, now 
up, now down, but this locomotion is by no means as rapid as 
when they are in contact with some object under water. Ordin- 
arily the two lateral sete are distended at an angle of about 
forty-five degrees, but during the swimming they are drawn in 
