112 



JOURXAL OF ECONOMIC ENTOMOLOGY 



[Vol. 8 



would lower the cost. T\lth six pairs, costing from S600 to S7o0, 

 six different temperatures could be maintained simultaneous!}^ and 

 the response of an insect to temperature under specified moisture 

 conditions determined in a short time. Furthermore, by the exclusion 

 of light or the use of artificial light of known composition and known 

 intensity, the disturbing influence of variable light could be eliminated. 



The machine just outlined by Mr. Dean seems realty to serve a 

 different purpose and not to be capable, except as its units are multi- 

 plied or modified, of lending itself to the study of insect response to 

 temperature and moisture. I say this because the number of cham- 

 bers is so small that any close determination of response with it must 

 involve the running of the temperature and moisture ranges of a single 

 insect in several successiA^e experiments, two degrees of temperature 

 or moisture being studied at a time, thus introducing another complex 

 variable. This apparatus does, however, provide a means of studying 

 insect life-history under known conditions of temperature and moisture. 

 It is also possible by use of smaller chambers within the larger ones to 

 run simultaneous^ a sufficiently large number of temperature or mois- 

 ture-response experiments to derive reliable, data on which to base 

 laws of response. 



Mr. G. a. Dean: In the discussion of the air-conditioning 

 apparatus I neglected to state the cost of instalHng the machine. The 

 total cost of the apparatus, including the breeding chamber and in- 

 stallation, is from SI, 600 to S1,80C. This is not an expensive apparatus 

 when 3^ou think of controlling the moisture and temperature in two 

 large chambers each 6x8x7 feet, or chambers large enough for a 

 man to enter and carry on his experiments. The machine, as the 

 illustrations show, is built for durability and should last for many j^ears. 



yin. F. C. Bishop: I should like to ask Mr. Dean about the 

 degrees of humidity. You say you have it at 6C degrees, but could 

 you maintain it lower? 



I\Ir. G. a. Dean: The most difficult control \yould be a low 

 humidity with a low temperature. There would be no difficulty in 

 maintaining either a low humidity or a high humidity with a high 

 temperature or a high humidity with a low temperature. If you 

 want a low humidity -^dth a low temperature, one bank of spra}^ noz- 

 zles should be turned off so that the relative humidity of the air passing 

 through the spraj^ chamber will be about 60 per cent. The tempera- 

 ture of the air will be \\dthin one degree of the temperature of the 

 spray water. When this air is passed to the heating chamber and the 

 temperature raised, the humidity will be lowered. If the temperature 

 and humidity are not low enough the air will have to pass through 

 colder water; for instance, one could use salty ice water. This water 



