Abstract
Eretmocerus warrae Nauman and Schmidt (Hymenoptera: Aphelinidae) is an important ecto-endoparasitoid of greenhouse whitefly Trialeurodes vaporariorum (Westwood) (Homoptera: Aleyrodidae). However, prior to the present study little was known about its life history strategies, making it difficult to develop a biological control program with this parasitoid. Using T. vaporariorum as hosts we carried out a series of experiments in the laboratory to determine the host stage preference by the foraging adults and its effect on the fitness of both adults and their offspring. The parasitoid females prefer to feed on and parasitize the second and third instar nymphs to gain maximal fitness for themselves and their offspring. Among the optimal hosts attacked, E. warrae allocate >80% of them for parasitization and <20% for feeding. The first instar larvae do not penetrate the host nymphs until the latter molt into the fourth instar regardless of the host stages parasitized. Therefore, after penetration all juveniles live in similar environment, feed on hosts with similar quality and quantity of nutrition, and achieve similar survival rate. The lower fitness gain and higher mortality of E. warrae juveniles when the first instar hosts are parasitized result from longer waiting time and starvation before penetration. The higher mortality of E. warrae juveniles if the fourth instar nymphs are attacked may stem from the fact that when E. warrae eggs hatch, the host nymphs have already developed to the pharate adult stage which the first instar larvae have difficulty penetrating.
Published Version
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