A non-dispersive infrared gas analyser equipped with a Luft-type sonic detector and flow-through reference cell was automated to monitor the total volume of carbon dioxide (COz) respired by single insects or groups of insects. The infrared analyser was interfaced with an integrator for quantification, a microprocessor to control intermittent air flow through the insect respiration chambers, and a microcomputer for data storage and reduction. This technique has been used to monitor the C 0 2 output of diapausing and non-diapausing mature fifth instar larvae and of developing pupae of the codling moth, Cydia pornonella (L.) (Lepidoptera: Tortricidae). The resulting data were accurate, quantitative and reproducible.