Female and Male Polymorphism in Two Species of Melittobia Parasitoid Wasps (Hymenoptera: Eulophidae)

Jorge M. González, Robert W. Matthews

Abstract


Polymorphism appears to be fundamental in Melittobia wasps, but uncertainty exists as to its extent and form. Most researchers recognize 2 basic female forms--a long-winged dispersive “type form” and an early-maturing, short-winged gravid “second form.” However, some investigators have recognized two macropterous forms, “jumpers” and “flyers.” Many others have suggested that males, which normally comprise only about 5% of the population, also may exist in 2 forms in various Melittobia species. This study examined the role of maturational factors in 2 widespread representatives of different species groups, M. australica (hawaiiensis group) and M. digitata (acasta group). Individuals of both sexes from different points in the emergence curve were examined and measured immediately after eclosion and 5 d later. Both sets of measurements supported the existence of 2 clearly defined female morphs. However, when newly eclosed macropterous females were randomly assigned to 5-d placements in empty vials or with prepupal hosts (Trypoxylon politum Say), subsequent tests in a flight arena demonstrated that “jumpers” and “flyers” were simple reflections of macropterous female physiological state, with heavier, gravid females reluctant to do more than a slow crawl, and lighter, more nutritionally stressed females being more inclined to fly. Thus we conclude that there is no justification for recognizing a “jumper” morph. Male morphometrics indicated continuous variability in size and pigmentation of simple eyes and ocelli, but no morphologically distinctive male morphs at any point in the emergence curve. However, reports of distinct male morphs in other Melittobia species cannot be dismissed.

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