Summary.Naphthalene vapour having been shown by other investigators to be toxic to Red Spider,Tetranychus telariusL., it was thought that better control of the fumigation would be obtained if the substance was vaporised by means of a lamp. A suitable lamp was designed and is described herein. It has been used under commercial conditions and has given satisfactory results.Carnations and tomatoes have been fumigated with naphthalene and satisfactory control of Red Spider has been secured as shown by data given herein.Fumigations on a variety of glasshouse plants in addition to the foregoing have been conducted and general observations and recommendations on naphthalene fumigation for the control of Red Spider are included.