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Physiology of the morphotype differentiation in the parasitic wasp Melittobia digitata (Hymenoptera, Eulophidae)

Dept. of Entomology, Texas A&M University, College Station, TX 77843-2475, USA

Morphotype differentiation has been shown to be under hormonal control in many species of insects, and hormonal changes may be triggered by many factors, such as population density. Melittobia digitata is a pupal ectoparasitoid of solitary wasps. This wasp can develop three wing morphotypes. Morphotype differentiation in this genus was associated with the clutch size, especially in the beginning of their development. The short-wing adults develop in small clutch sizes. These adults will continue in the nest to explore the remaining of the host. On the other hand, the long-wing will develop in large clutch sizes, and the host will be completely fed. These wasps have to disperse, and find a new host to lay their eggs. These morphotypes also vary in the ovarian function. The short-wings are provigenic while the log-wings are synovigenic. We have demonstrated that the morphotype differentiation in M. digitata is dependent on the nutritional quality of the host resource that has being exploited. The proportion of the short-wing adults will decrease in proportion to the availability of the host hemolymph as a food resource. Soon they have to start feeding on the tissues of the host, more of the long-wing type will develop. The role of hormones on the morphotype differentiation of M. digitata and mechanisms of nutritional control of hormone levels will be discussed.

Index terms: nutritional requirements, hormones, oogenesis, vitellogenin, host feeding

Copyright: The copyrights of this abstract belong to the author (see right-most box of title table). This document also appears in Session 13 – INSECT PHISIOLOGY, NEUROSCIENCES, IMMUNITY AND CELL BIOLOGY Symposium and Poster Session, ABSTRACT BOOK II – XXI-International Congress of Entomology, Brazil, August 20-26, 2000.