Myiasis has been defined by Austen as follows:—“There remains yet a third category of flies, chiefly belonging to the great Family Muscidae, the larval stage of which is sometimes actually passed in the living human body, the presence of the larvae in the various organs and tissues, and the disorders or destruction of tissue caused thereby, being comprehensively known as Myiasis.” It will be noted that this definition only refers to the larval stages of flies, but as the eggs, and in one case at least, pupae and adults, may be found in the human body, and as myiasis is a common condition in many animals, the definition may now be amplified as follows:— The condition or conditions, resulting from the invasion of the tissues and organs of man and other animals by all the stages of the Diptera.