408 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1919. 
during the shedding and disappear from the outside of the slough, 
though the holes where they were pulled in can be found before the 
membrane becomes too dry. 
The nymph usually runs about at first in the groove of the twig 
containing its egg nest and then goes out on the smooth bark. Here 
any current of air is likely to carry it off immediately, but many 
wander about for some time, usually going toward the tips of the 
twigs, some even getting clear out on the leaves. But only a few 
nymphs are ever to be found on twigs where hundreds have recently 
hatched, as shown by the piles of embryonic skins; so it is evident 
that the great majority either fall off or are blown away very shortly 
after emerging. Many undoubtedly fall before the shedding of the 
egg membrance, for the inclosed creature has no possible way of 
holding on and even the free nymph has but feeble clinging powers. 
Those observed on twigs kept indoors often fell helplessly from the 
smooth bark while apparently making real efforts to retain their 
grasp. Their weak claws could get no grip on a hard surface. In- 
stead, then, of deliberately launching themselves into space in re- 
sponse to some mysterious call from below (as usually described) 
the young cicadas simply fall from their birthplace by mere in- 
ability to hold on. But the same end is gained—they reach the 
ground, which is all that matters. Nature is ever careless of the 
means so long as the object is attained. Some acts of unreasoning 
creatures are assured by the giving of an instinct, others are forced 
by taking away the means of acting otherwise. 
The cicada nymphs, like young scales, are at first attracted by the 
light. Those allowed to hatch on a table in a room left the twigs 
and headed straight for the windows 10 feet away. This instinct 
under natural conditions serves to entice them toward the outer 
parts of the tree, where they have the best chance of a clear drop to 
earth; but even so, adverse breezes, irregularity of the trees, under- 
brush and weeds can not but make their downward journey one of 
many a bump and slide from leaf to leaf before the earth receives 
them. 
The creatures are too small to be followed with the eye as they 
drop, and so their actual course and their behavior when the ground 
is reached are not recorded. But several hatched indoors were placed 
on loose earth packed flat in a small dish. These at once proceeded 
to get below the surface.. They did not dig in but simply entered the 
first crevice that they met in running about. If the first happened 
to terminate abruptiy, the nymph came out again and tried another. 
In a few minutes all had found satisfactory retreats and remained 
below. The avidity with which they dived into any opening that pre- 
sented itself indicates that the call to enter the earth is instinctive and 
