The author in this interesting and in parts humourously written article first of all gives a brief survey of the literature on Instincts from the theological, the mechanistic or physiological, and the psychological or anthropomorphic points of view. He then says that the methods of investigating instincts may be treated under three heads, the experimental, the historical and the psychopathic. He goes on to show how the experimental method supplemented by the historical can be applied in the interpretation of behaviour in three typical insect instincts, namely, the spraying instinct of the Formica rufer, the balloon-making instinct of the Empidid flies and the spinning instinct of the caterpillars of moths and butterflies. He considers that the third method, the psychopathic, is the one that promises important results.