Upon initiating a research project on the role of volatile infochemicals in the tritrophic system Cotesia
(=Apanteles) glomerata (L.) - Pieris brassicae (L.) - cabbage, a bioassay was developed to investigate
the response of C. glomerata. The bioassay should be effective in terms of high responsiveness and
minimum variability and constructed through a comparative approach. Twenty seven treatments, organized
in a factorial randomized block design, compared the effect of three bioassay set-ups (glasshouse
flight chamber, wind-tunnel and Y-tube olfactometer), three parasitoid age groups (1-2, 4-5 and 8-9
days old females), three pre-treatment experiences (naive, damage experienced and oviposition experienced
wasps) and the day-to-day effect on response of C. glomerata to clean cabbage (CC) and planthost
complex (PHC) in a dual choice test.
The best results with regard to the strength and consistency of response to the PHC were obtained
in the glasshouse flight-chamber by 4-5 days old female wasps with either damage or oviposition experience
(94 and 90~ respectively). It is therefore recommended as a suitable bioassay for studying the
role of volatile infochemicals in host-habitat location by C. glomerata.
A day-to-day variation in response was found in the glasshouse and wind-tunnel. It was correlated
with the direction of change in barometric pressure within the time period of the experiment, showing
that steadily increasing atmospheric pressure yields a significantly higher response than steadily decreasing
or fluctuating barometric flux. To control for the day effect it is suggested to conduct further
experiments in a block design, having day as a block. Several aspects of the infochemical ecology of
C. glomerata are discussed.