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J. HYM. RES. Vol. 4, 1995, pp. 110-120 Ovipositor Steering Mechanisms in Braconid Wasps Donald L. J. Quicke, Mike Fitton, Jane Harris (DLJQ) Department of Biology, Imperial College at Silwood Park, Ascot, Berks SL5 7PY, U.K.; (MF, DLJQ) Department of Entomology, The Natural History Museum, London SW7 5BD, U.K.; (JH) Department of Animal and Plant Sciences, PO Box 601, University of Sheffield, Sheffield SIO 2UQ, U.K. Abstract. — Ovipositor features which allow the ovipositor tip to be manipulated and which have restricted distributions among the subfamilies of Braconidae are described and illustrated for the first time. Members of the Amicrocentrinae, Charmontinae, Helconinae and Macrocentrinae have the rhachis (the tongue-like part of the mechanism that interlocks the upper valve with the lower ones) with an increased density of scale-like sculpture and often also swollen pre-apically. This modification leads to increased friction and restricted movement between the upper and lower valves and is also associated with an ovipositor bending mechanism in which retraction of the lower ovipositor valves relative to the upper one causes the ovipositor tip to bend ventrally. Many members of the subfamilies Agathidinae and Orgilinae possess a pair of pre-apical boss-like pro-jections on the upper ovipositor valve (gonapophyses 9) and a corresponding structure on each lower valve (gonapophyses 8) that together enable the wasps to bend and manipulate the ovi-positor apex by retraction of the lower ovipositor valves relative to the upper one. Most members of the Doryctinae have the aulax (the groove-like part of the mechanism that interlocks the lower valve with the upper one) constricted opposite modified pre-apical, dorso-lateral tooth-like struc-tures. These constrictions restrict the relative movement between the upper and lower valves and thus operate as an ovipositor bending mechanism. The potential phylogenetic significance of these mechanisms is discussed, and preliminary parsimony analyses are described which suggest that the pre-apical boss-like projections of the Agathidinae and Orgilinae may represent a synapo-morphy uniting these two subfamilies. INTRODUCTION Oviposition behaviour and, as a conse-quence, the ovipositor have been of im-mense importance in the evolution of the Hymenoptera, and are central to the par-asitic way of life (Gauld & Bolton 1988). The commonly held vievv^ that the ovipos-itors of parasitic w^asps are fairly simple analogues of hypodermic needles is there-fore likely to be a considerable over-sim-plification as has in fact been shown by several previous investigations of func-tional morphology (Oeser 1961; Austin & Browning 1981; Quicke et al. 1992a,b, 1994). Several braconid genera have recently been shown to possess highly modified ovipositors whose tips are capable of be-ing independently actively manipulated by the wasp even though the ovipositor valves themselves are devoid of intrinsic musculature and their relative movements are controlled by muscles within the me-tasoma. Mechanisms, as found for exam-ple in the braconine genus Zagli/ptogastra Ashmead, were apparent because of very conspicuous features of the intact ovipos-itor (Quicke 1991; Quicke & Marsh 1992). However, an ability to manipulate or steer the ovipositor tip has been observed in a number of other parasitic Hymenoptera whose ovipositors appear more or less un-modified externally (Delanoue & Aram-bourg 1965; Compton & Nefdt 1988). Fur-ther, our own observations have also

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Ovipositor steering mechanisms in braconid wasps

D L J Quicke, M G Fitton and J Harris
Journal of Hymenoptera Research 4: 110-120 (1995)

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