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Larval morphology of Metaphycus flavus and its role in host attachment and larval cannibalism

Published online by Cambridge University Press:  06 January 2011

A. Tena ,
A. Kapranas ,
G.P. Walker ,
F. Garcia-Marí  and
R.F. Luck
A. Tena*
Affiliation:
Unidad Asociada de Entomología IVIA-UJI-CIB, Instituto Valenciano de Investigaciones Agrarias, Spain
A. Kapranas
Affiliation:
Department of Entomology, University of California, Riverside, USA
G.P. Walker
Affiliation:
Department of Entomology, University of California, Riverside, USA
F. Garcia-Marí
Affiliation:
Instituto Agroforestal del Mediterráneo, Universidad Politécnica de Valencia, Spain
R.F. Luck
Affiliation:
Department of Entomology, University of California, Riverside, USA
*
*Author for correspondence Fax: (+34) 96 342 40 01 E-mail: [email protected]
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Abstract

Metaphycus flavus (Howard) (Hymenoptera: Encyrtidae) is a facultatively gregarious endoparasitoid of soft scales (Hemiptera: Coccidae). When it develops in superparasitised hosts, the larvae often attack and consume brood mates six or more days post oviposition. Under our laboratory conditions (25±1°C and 14 hours of light followed by 18±1°C and ten hours of darkness in 50–70% R.H.), M. flavus eggs hatched three days after oviposition. Measurements of the mandibles and tentorium indicate there are four larval instars, and M. flavus reaches the fourth instar by day six post oviposition, and pupates on day eight. Thus, cannibalism among M. flavus larvae occurs during the fourth instar. During this instar, M. flavus larvae separate from their attachment to the scale cuticle, to which they were tethered by a respiratory structure during the previous three larval instars. Once detached, they are free to move within the scale, which increases the probability of larval encounters and aggressive behaviours. Moreover, the mandibles of the fourth instar are better adapted for fighting than are those of the first three larval instars, since they are larger and more sclerotized. The cranium and mouthparts of M. flavus have four different types of sensory organs, some of which are almost certainly olfactory, an unexpected function for a larva that presumably is surrounded by an aqueous medium where gustatory sensilla would seem to be more appropriate. The cranium also bears two pairs of what appear to be secretory pores.

Keywords

Encyrtidaesoft scaleslarval developmentsuperparasitismintraspecific competitionsensilla
Type
Research Paper
Information
Bulletin of Entomological Research , Volume 101 , Issue 3 , June 2011 , pp. 365 - 372
Copyright
Copyright © Cambridge University Press 2011

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