This work surveys the biology and wartime significance of small invertebrates that afflict soldiers and camps, including lice, fleas, bedbugs, flies, moths, mites, ticks and leeches. It explains life cycles, habits, modes of transmission and how these pests spoil food, spread disease, injure skin and undermine unit health. Illustrations and practical advice on prevention, sanitation and control accompany the descriptions, aiming to inform medical officers and lay readers about measures to protect troops and reduce the non-combat causes of illness and discomfort.