Insects as a group occupy a middle ground in the biosphere between bac teria and viruses at one extreme, amphibians and mammals at the other. The size and general nature of insects present special problems to the student of entomology. For example, many commercially available in struments are geared to measure in grams, while the forces commonly en countered in studying insects are in the milligram range. Therefore, tech niques developed in the study of insects or in those fields concerned with the control of insect pests are often unique. Methods for measuring things are common to all...