Effect of Adult Experience on the Host-Location Behavior of the Aphid ParasitoidAphidius colemaniViereck (Hymenoptera: Aphidiidae)

We investigated the relationship between age and learning ability of femaleAscogaster reticulatusWatanabe, an egg-larval parasitoid of the smaller tea tortrixAdoxophyessp. (Lepidoptera: Tortricidae). Females 1, 3, 5, 7, 9, 11, and 13 days old had higher fecundity than 0-day-old females and could associate tea leaf extract with the host egg mass through oviposition. Experienced females 1 ≈ 13 days old walked more than 10 cm along an extract-treated line while exhibiting the antennating response. However, the learned responses of 0-day-old females was significantly lower mean = 1.4 ± 0.8 (S. E.) cm] than that of older females (1 ≈ 13 days). In considering the relation between fecundity and the learned response, a low response in 0-day-old females could be due to a low propensity by them to learn cues associated with host eggs. Average longevity was 12.0 ± 1.5 days, but even 13-day-old females could oviposit a large number of eggs and learn to associate the tea leaf extract with host presence. This suggests that females can learn as long as they are able to oviposit. This learning ability would be advantageous forA. reticulatusfemales throughout their lives.