This paper calls attention to the habit of certain insects of passing their legs and antennae between their mouth parts and the removing of powdered materials in this manner. This habit of the insects, the writers have termed the natural “cleaning up” habit of certain insects. A brief review of some of the literature on this subject is given. An attempt is made to distinguish cleanliness from irritation as the cause of the stimulation of this action. The following insects have been stimulated to this natural “cleaning up” habit in our experiments: Diabrotica soror, Blatella germanica, Forficula auricularia, Syneta albida, and Criocerus asparagi. Several of the following dusts have stimulated the “cleaning up” with each of the above insects: Sodium fluoride, calcium arsenate, lead arsenate, sodium fluosilicate, wheat flour, and powdered milk sugar. The methods used in the experiments are briefly explained.