SEVENTEEN- YEAR LOCUST SNODGRASS. 387 
with the claw-like tips of the front tibiae. Thus the change in the 
feet is significant in connection with the change in habits, though, as 
has been shown, the long tarsi of the mature pupa play an important 
part in its digging also. 
Early in the spring, hefore the proper emergence season, pupae 
are often found beneath logs and stones. This is to be expected — to 
the ascending pupae the surface is at the top of the log or the top 
of the stone. As thej' burrow upward something impenetrable blocks 
their paths, and that is all. But a more curious thing often observed 
is that, in some localities, the insects continue their chambers up 
above the surface of the ground within closed turrets of mud several 
inches high. Where these towers occur it is likely that there is some- 
thing about the nature of the soil that the insects do not like; per- 
haps it is wet and the normal chambers are damp and moldy or 
partly filled with water. The writer had no opportunity to study 
the turrets since none were to be found at Somerset. The most in- 
teresting description of them is that given by Dr. J. A. Lintner in 
his Twelfth Report on the Insects of New York, published in 1897. 
Doctor Lintner states that " The chambers are constructed by the 
pupae with soft pellets of clay or mud brought up from below and 
pressed firmly into place," and he records that Mr. I. H. Lawton 
caught a pupa at work with a pellet of mud in its claws. Hence, we 
may infer that, as a mason, the cicada's style of work is only a modi- 
fication of its working methods as a miner. Yet what an interesting 
sight it would be to watch the actual building of one of these adobe 
huts. At emergence time the towers are opened at the top and the 
insect comes forth as it would from an ordinary chamber opening at 
the level of the ground. 
TRANSFORMATION. 
By some feeling of impending change the pupa, waiting in its 
chamber, knows when the time of transformation is at hand. Some- 
how nature regulates the event so that it will happen in the evening, 
but once the hour has come no time is to be lost. The pupa must 
break out of its cell, find a suitable molting site and one in accord 
with the traditions of its race, and there fix itself by a firm grip of 
the tarsal claws. At the beginning of the principal emergence period, 
about the 21st of May, large numbers of the insects came out of their 
chambers as early as 6 o'clock by " daylight-saving time," which 
would be 5 o'clock by standard time ; but after the rush of the first 
few days not many appeared before dusk. 
It is difficult to catch a pupa in the very act of making its exit from 
the ground, and apparently no observations have been recorded on 
the manner of its leaving. At Somerset, in spite of closest scrutiny 
