LIBRARY 
 STATE PLANT BOARD 
 
 July 1%6 ET-230 
 
 . United States Department of Agrioulture 
 I Agricultural Research Administration 
 Bureau of Entomology and Plant Quarantine 
 
 A SIMPLE CAGE FOR TESTING DDT RESIDUAL TREATMENTS l/ 
 
 By A. H. Madden and Arthur W. Lindquist 
 Division of Insects Affecting Man and Animals 
 
 It frequently becomes necessary to determine whether surfaces 
 that have been treated with DDT retain a deposit of this insect ioide, 
 and the approximate toxicity of the deposit, Sinoe it is not possible 
 to make ohemioal analyses of suoh deposits, a biological assay method 
 oan be utilized. The following method was developed in 1943 at the 
 Orlando, Fla., laboratory of this Bureau during the course of studies 
 on DDT residues on the interior surfaoes of treated airplanes. 
 
 A shallow oage (fig. 1) suitable for exposing houseflies or 
 mosquitoes to surfaoes treated with DDT may be constructed easily 
 from the cover of a wide-mouth Mason jar. The metal center of the 
 cover is replaced by a disk of 16-mesh screen wire (a finer mesh 
 may be needed for certain species of mosquitoes), which is soldered 
 in plaoe. A thin block of wood is fastened across the outer side 
 to serve as a handle and support. A metal disk, with a narrow strip 
 of metal soldered around a small section of the edge, serves as a 
 oover for the open side of the oage. 
 
 When houseflies ( Musoa domestioa L.) are to be used as the test 
 insects, the cage is filled by placing it over an opening in the top 
 of a large cage of houseflies. When the desired number have entered, 
 the metal disk is slid into place (fig. 2). To load with mosquitoes 
 the oage is introduced into a large cage containing hundreds of these 
 insects and dapped against a surfaoe on which they are congregated. 
 The metal disk is then slid into plaoe. With the metal disk held 
 firmly by rubber bands, the cages may be transported or stored for 
 24-hour mortality counts. 
 
 To conduct a test, the cage filled with inseots is placed against 
 a treated surface, the metal disk removed, and the cage secured by 
 stretching a rubber band between two small nails (fig. 3) or other 
 supports. For use in an airplane the rubber band is stretched between 
 battery clamps clipped to the ribs. At the end of the exposure period, 
 
 l/ This work was oonducted under a transfer of funds, recommended 
 by the Committee on Medical Research, from the Office of Soientifio 
 Research and Development to the Bureau of Entomology and Plant 
 Quarantine. 
 
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 the metal disk is slid into place and the cage removed. If the insects 
 are to be held for 21 hours, a drop of honey and a bit of water-soaked 
 cotton placed on the outside of the screen wire will provide them 
 with food and water. 
 
 Knock-down or mortality counts may be taken readily through the 
 screen. when all records are completed, the remaining live insects 
 may be killed by placing the cages in an electric oven for a few 
 minutes. This makes it possible to determine the total number of 
 insects per cage. Unexposed check insects will remain alive in this 
 type of cage for 24. hours or more when fed and watered and held at a 
 temperature of 780-82° F. 
 
 I 
 
 Figure 1. — Exposure Cage Showing Slide. 
 
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 Figure 2. — Loading exposure cage with houseflies. 
 
 Figure 3. — Exposure cage in place. 
 
UNIVERSITY OF FLORIDA 
 
 ilium ii mil! 
 
 3 1262 09240 8870