a1 Department of Entomology, London School of Hygiene and Tropical Medicine
1. The growth and development of normal and sterile (i.e. symbiont-free) Rhodnius prolixus are compared. The last three instars of sterile bugs weigh less than normal ones. Sterile insects completed the first three stages of their life-histories in less time than normal insects, and at the fourth stage, nutritional deficiencies had profound effects on their further development.
2. The sensitivity of the Rhodnius symbionts, Nocardia rhodnii, to five antibiotic substances is determined. Terramycin, aureomycin and chloramphenicol are effective inhibitors.
3. The symbiotic condition in Rhodnius and the related bug, Triatoma infestans, is discussed.
(Received July 27 1959)
p1 Present address: South African Institute for Medical Research, P.O. Box 1038, Johannesburg, South Africa.