Mar. 20,1916 Temperature and Humidity and Insect Development 1185 
As the temperature continues to rise it passes through a zone of 
ineffective temperatures, known commonly as the zone of hibernation, 
which the writer will shortly prove to be an inappropriate term. At the 
lowest temperatures in this zone complete dormancy without metab¬ 
olism is found; but as the temperature increases a gradual approach to 
sensibility is noted, first metabolism, next movement, and then the 
necessity of feeding. The point at which metabolism or growth begins 
at a given humidity is the zero of effective temperature. 
As the temperature increases above this zero the activity is at first 
very sluggish, but becomes more and more active until the so-called 
optimum is reached, and from this point upward the temperatures cause 
less and less activity, inducing stupor and finally sleep or coma. 
At the point of coma begins the zone of ineffective temperatures 
formerly known as estivation. With the increase of temperature sleep 
becomes more and more sound until a point is reached at which death 
oceurs after long exposure. At this point begins the zone of high fatal 
temperatures at which death occurs at shorter and shorter periods until 
it is instantaneous at the absolute maximum fatal temperature. This 
completes the vertical cross section of the figure desired. A statement 
regarding these vertical zones was first published by the Bureau of 
Entomology in 1912. 1 
In the past, however, the fact that a similar horizontal cross section 
at any temperature can be made, starting at absolute dryness and reading 
toward absolute humidity, has not been recognized. In this manner are 
shown zones of fatal dryness, dryness causing stupor, increasingly effective 
humidity, the most effective humidity, decreasingly effective humidity, 
excessive humidity causing drowsiness, and finally fatal humidity, at 
least under certain conditions of exposure. 
In the case of the boll weevil the resulting figure is a series of con¬ 
centric ellipses centered about the optimum and with diagonal axes. 
On the accompanying diagram the main details of the relations of tem¬ 
perature and humidity to the boll weevil are brought out. Only a few 
of the more salient records are included. The development in buds 
(cotton squares) is based upon hundreds of individual records, but is not 
reported in detail. The outer lines are much less definitely located 
than the inner ones, but whatever their actual location the picture 
would be substantially the same. 
EFFECTIVE TEMPERATURE 
Workers who have used the zero of effective temperature in their 
studies will note that, according to the present theory, the zero when 
charted is an elliptical curve representing a different point at each degree 
1 Hunter, W. D., and Pierce, W. D. Mexican cotton-boll weevil. 62d Cong., 2d Sess., Sen. Doc. 305 
(U. S. Dept. Agr. Bur. Bnt. Bui. 114), p. 125-128. 1912. 
27467°—16 - 4 
