48 
DR ALFRED E. CAMERON. 
Entomologists, December 1914, Dean and Nabours* described a new air-condi- 
tioning apparatus for maintaining a desired constant humidity and temperature 
within a reasonable degree of variation. If in nothing else, it does not lack 
elaborate structure. The principle seems to consist in passing a current of air 
through a spray chamber, where it acquires a certain degree of relative humidity 
depending on the temperature of the water. It then passes over a thermostat, 
where there is imparted to it the required change of temperature before entering 
the breeding chamber. Dr Headlee, with whom the author has had the 
opportunity of discussing the subject, described at the same meeting - a simple 
apparatus for the same purpose, consisting of constant temperature and moisture 
incubators. It is his opinion t “ that the response of insect protoplasm, as exhibited 
in variations of the rate of metabolism, appears to depend upon : (l) where in the 
particular insect’s temperature range the temperature changes occur ; (2) the type 
of metabolism characteristic of the insect, when the response (to temperature 
change) is taken ; (3) the presence of any abnormal factor such as parasitism.” 
The third of these is of peculiar interest, and, if neglected, might lead to an 
apparent discrepancy in the results. Quoting Davenport, he further emphasises 
( loc . cit. p. 416) the effect of moisture on insect metabolism, where, according as 
the amount of moisture is increased, growth increases until an optimum is reached. 
The quantity available does not determine the amount imbibed, which is rather 
controlled by the needs and habits of the species. 
Shelford | is of the opinion that the best and most accurate index of the 
varying physical conditions surrounding land animals wholly or partly exposed to 
the atmosphere, is the “ evaporating power of air.” The standard of measurement 
is expressed by the amount of water which the atmosphere, under different con- 
ditions of air-temperature, pressure, relative humidity, and average wind velocity, 
absorbs from a free water surface in a given time. Evaporation is greatest in open 
associations, as has been demonstrated by Transeau,§ where the absence of dense 
vegetation permits of the more rapid removal of water vapour. By means of the 
porous cup atmometer, as devised by Livingston, || quantitative evaporation experi- 
ments can be successfully carried out. 
The significance of the evaporation aspect is likely to prove so important that 
Shelford’sIT conclusions, deduced from the results of a series of experiments on the 
reaction of various animals to atmospheres of different evaporation capacities, may 
* Dean, G. A., and Nabours, R. K., “A New Air-Conditioning Apparatus,” Jour. Econ. Ent., vol. viii, No. 1, 
pp. 107-111. 
t Headlee, J., “Some Data on the Effect of Temperature and Moisture on the Rate of Insect Metabolism,” 
Jour. Econ. Ent., 1914, vol. vii, No. 6, p. 414. 
| Shelford, Y. E., “ Animal Communities in Temperate America,” Geog. Soc. Chicago, Chicago, 1912, p. 161. 
§ Transeau, E. N., “ The Relation of Plant Societies to Evaporation,” Bot. Gaz., pp. 217-231. 
|| Livingston, B. E., “The Relation of Desert Plants to Soil Moisture and Evaporation,” Publ. No. 50, 
Carnegie Institution. 
IT Shelford, V. E., loc. cit. p. 163. 
