It is a matter of general agreement that atmospheric humidity is often of great importance in limiting the times or places at which insects are abundant. But though one may collect facts which suggest that a particular degree of dryness or dampness favours some stage of an insect, it is not easy to devise experiments which will give unassailable facts. Some of us feel that the precise study of water relations and water balance may lead to greatly increased knowledge of the living insect, and therefore to results of economic value ; and it is certain that a fuller understanding of these matters is delayed because few know the methods appropriate for measuring and controlling humidity. The purpose of the present paper is to make known a number of practical methods, which might be of service to a worker even in a remote country. As this is my objective, I shall include material which is already well known to physicists, and as our concern is with the conditions in the places where insects are actually living, I have given particular attention to unorthodox devices which can be used in small spaces and which are portable; among the great variety of methods, I have endeavoured to show what is good and bad in each.

The Measurement and Control of Atmospheric Humidity in Relation to Entomological Problems.

PREVIOUS workers who have investigated the conditions of temperature and humidity beneath the shirt, have done so mainly in relation to the hygiene of clothing. Towards the end of the last century, Rubner and his colleagues did some work bearing on this problem. In the course of investigations connected with clothing, the temperature and humidity of the air beneath it were measured. Rubner and von Lewaschew (1896) made use of a small composite thermometer and hair hygrometer, which had been designed by Lambrecht. This apparatus needed frequent recalibrations, and was satisfactory only within narrow limits, so that I think the results obtained must be regarded with caution. They found that the relative humidity of the air beneath the shirt was often as low as 25 per cent., and that its temperature rose as the external temperature became higher, or the external air moister. They found the temperature to be higher than either Leonard Hill or I have found under similar conditions, probably because the thermometer was enclosed in the apparatus and protected from cooling. The nature of the clothing has a great influence on the loss of heat and moisture from the skin. Kratschmer (1896) gives tables showing the amount of moisture taken up by various fabrics, but it appears that we know nothing of the effects of materials on the humidity conditions of the air enclosed. This subject has been touched on by Leonard Hill (1914) whilst dealing with problems of industrial hygiene. He used a wet and dry-bulb thermometer to investigate the conditions under the shirt. The main objection to this method is that unless the wet bulb is in a current of air (which it was not), the reading is inaccurate, and will show too high a relative humidity. Also, the wet bulb will give off moisture into the enclosed space and raise its humidity. His results show considerably higher humidities than Rubner or I found under similar conditions, but the dry-bulb temperatures are in agreement with my results. The air under the shirt appears to have a slightly higher CO2 content than the air outside. Kratschmer (1896) showed that when the outside air has about 004 per cent. carbon dioxide, the air under the shirt has about 0-08 per

/pdf/the-conditions-of-temperature-and-humidity-of-the-air-1felda00qs.pdf

The Conditions of Temperature and Humidity of the Air between the Skin and Shirt of Man.

Eric Keightley Rideal was born on 11 April 1890 at Sydenham, the son of Samuel Rideal, D.Sc., F.I.C., and Elizabeth (Lilia) nee Keightley, the daughter of Samuel Keightley, J.P., of Bangor, Co. Down.

https://royalsocietypublishing.org/doi/pdf/10.1098/rsbm.1976.0017

A. Hannah

Papers

A new chemical hygrometer