The 2^nd, 3'd instar larvae, 3 and 8 days old pupae of the onion bulb fly, E.
vestitus were exposed to 3 different concentrations of CO₂ in air for 24, 48 and 72 hr.
The rate of mortality in all treatments was positively correlated with C02-concentration
air and the exposure period . Treatments of the 2^nd and 3'd instar larvae resulted
increasing the larval duration while the rate of pupation was reduced by increasing the
C02 concentration and/or the exposure period. Also, the pupal duration was increased
while the rate of adult emergence was greatly reduced. Treatments of 3 and 8 days old pupae resulted increasinq the pupal
duration but the percent of adult emergence was decreased by increasing the C02
concentration and/or the exposure period. In general, the pupae were more tolerant
than the larvae and the 8 days old pupae were more sensitive than the 3 days pupae.