Mar. ao, 1916 Temperature and Humidity and Insect Development 1189 
From these tables it will be seen that the effective period of develop¬ 
ment is from 8 to 10 days, averaging 8.43 days, while the actual develop¬ 
ment ranged from 13 to 16 days. It is noticeable that in all of the 
records the maximum as well as the minimum temperatures ran outside 
of the zone of effective temperatures. The total effective temperature 
ranged from 72 0 to 83° F., with 73.3 0 as the weighted mean and with a 
total difference of only 10.84°, a vel 7 small difference. 
It is not necessary in this paper to give the further details of the zone of 
effective temperatures ^at other humidities. The determination of the 
zone for the next percentage of humidity is much less difficult, because it 
must be just a little narrower or a little wider than already determined. 
As the axis is diagonal, the upper and lower bounds will depart at a 
different rate. After several points have been determined, the axis can 
be located and then the figuring becomes very simple. It must be noted 
that every hour of effective temperature has its cumulative effect, even in 
the winter time. 
ZONK OF INACTIVITY 
One of the results of the acceptance of the present interpretation will be 
the necessity of discarding the conception of separate zones of hibernation 
and estivation. Physiologists have demonstrated that the effects of heat 
and cold on metabolism are alike. The writer has frequently noticed in 
field work the impossibility of differentiating between a frozen and a heat- 
killed boll-weevil larva. Prof. G. G. Becker, of Arkansas Agricultural 
College, several years ago observed that the fall army worm, Laphygma 
frugiperda S. and A., had two periods of activity and two of inactivity 
every day in the hot days in the Ozarks. Activity began in the moor¬ 
ing and continued until the early part of the afternoon, when the heat 
caused the worms to be inactive for several hours. They then again 
became active during the early hours of the night, but the nights were 
cold and the worms became inactive until morning. The phenomena 
of a year were reproduced day by day. Inactivity due to cold in the 
summer time can not properly be called hibernation. 
In Arizona the boll weevil is now native on wild cotton (Thurberia 
thespesioides ). It normally breeds in the bolls in "he fall, becoming adult 
by December 1, but remains in its cell throughout the cold winter and the 
vanning spring. In some canyons there is a spring rainy season and T. 
thespesioides has a spring fruiting season. In these localities the moisture 
also releases the weevils from their cells and they begin breeding. A dry 
season follows and the weevils go to sleep. In other canyons the spring is 
not wet and the plants and weevils are inactive until the regular rainy 
season in August, when the long rest is broken. In some canyons the 
weevils therefore have two resting periods during the year, and in other 
canyons they are at rest from fall until summer. It not infrequently 
happens that the August rainy season does not materialize, and under 
