Effect of nymphal diet on adult predation behavior in Orius majusculus (Heteroptera : Anthocoridae)

The predatory bug Orius majusculus (Reuter) was reared on 2 different diets during the nymphal stages. The ist group was exclusively offered eggs of E phestia kuehniella Zeller (Lepidoptera: Pyralidae), a standard diet for O. majusculus production The 2nd group was exclusively offered 4th instars of the pea aphid, Acyrtosiphon pisum (Harris). Subsequently, adult predatory b ehavior in experimental arenas containing A. pisium was recorded using 2 vi deo cameras. One camera permitted observation of the predator's contact wit h the prey, where the 2nd camera viewed the arena from above to record the path taken by O. majusculus adults before and after contact with prey. When O. majusculus were reared on aphids, adult bugs successfully located and c onsumed 55% of experimental prey and continued prey search behavior after e ach al,hid meal. O. majusculus adults that had no experience of aphid preda tion as nymphs, did not prey on aphids in the experimental arena The mean w alking speed of this group of predators increased from 5.9 +/- 1.2 mm/s to 9.8 +/- 0.7 mm/s after contact or detection of prey, indicating that predat ors rapidly moved away from unfamiliar prey. Moreover, for egg-reared O, ma jusculus, all contacts between aphid and predator were lateral, along the s ide of the prey and were effectively repelled by an aphid kicking response. In contrast, 83% of attacks by aphid-reared O, majusculus were directed at the head or posterior abdomen for which the prey could not defend themselv es adequately. When egg-reared O. majusculus were exposed to novel aphid pr ey for 1-8 d, the frequency of aphid attack increased significantly. We con clude that the standard diet used for rearing O. majusculus may adversely a ffect the efficiency of this predator as an agent of biological control.