The Measurement and Control of atmospheric Humidity in relation to Entomological Problems

Abstract

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

“…2 is that I am interested in the conditions as they apply to insects, especially Pediculus humanus corporis. We have reason to believe that the loss of water by insects is proportional to the saturation deficiency of the air (Buxton, 1931 a) at different temperatures. This has not yet been definitely proved, but certainly the rate of loss of water is much more nearly proportional to the saturation deficiency of the air than it is to the relative humidity.…”

Life History, Non-Specificity, and Revision of the Genus Chorioptes, a Parasitic Mite of Herbivores

“…Paraffin in the bottom of the jar was at least a centimeter deep, and contained appropriate excavations for holding about 10 vials. A solution of sulphuric acid on the paraffin maintained the relative humidity at 80% according to the data of Buxton (1931). The relative humidity was checked from determination of the specifie g ravity of the solution, and by use of a dew-point of the mites to a small area on an otherwise negative cow.…”

Saturated Solutions For the Control of Humidity in Biological Research

“…Dessens (1946) describes a method by which the R.H. can be estimated by changes in the diameter of drops of LiCl solutions. Ludwig and Anderson ( 1942) adapted a suggestion by Buxton (1931) using the gain in weight of an hygroscopic organic material. They dried small (50 mg) pieces of gelatin to constant weight and then calibrated these over known solutions of KOH (see below).…”

“…The following lists of saturated solutions and humidities, gathered primarily from the literature, are quite complete and should provide a good range of conditions for ecological and physiological work. Data of this sort have been incomplete and inadequate in the biological literature (Buxton andMellanby 1934 andSolomon 1951), and most of the recent material has been published in chemical and trade journals which are not commonly used by biologists (cf. O'Brien 1948, Wink and Sears 1950, Richardson and Malthus 1955. Many of the relative humidity values presented in earlier works (e.y.…”

“…Sweetman 1933, Janisch 1938 are not accurate because of the use of impure salts and questionable methods. For excellent discussions of the basic concepts and problems of humidity, vapor pressure, etc., the reader is referred to Buxton (1931), Edney (1957), and Beament (1958).…”