Department of Biology, Laval University, Ste. Foy, QC. G1K 7P4, Canada.
Mating in the aphid parasitoid, Aphidius nigripes is modulated by a long distance female pheromone. Under controlled conditions in a wind tunnel we initially examined the effect of wind speed and distance from the source (10 virgin females) on the response of virgin males. At a wind velocity of 100 cm/sec males generally did not initiate flight, and those that did rarely reached the source. At lower velocities male responsiveness generally declined as the distance from the source increased, although the distance effect was minimal at wind speeds approaching the upper threshold. Similar patterns were observed when we tested the attractiveness and responsiveness of different sized females and males (the result of different host sizes), with no clear effect of body size. There was a very noticeable day to day variability in the proportion of males responding, when all other factors were held constant. This was associated with fluctuations in atmospheric pressure in the 24h preceding the assay. The importance of these abiotic and biotic factors on the reproductive biology of this parasitoid will be discussed.