On some behavioural strategies in Eulophid ectoparasitoids ( Hymenoptera, Chalcidoidea)

Abstract

The Authors refer on some behaviour regarding the adults and the prepupal phase
of Eulophid ectoparasitoids (Hymenoptera, Eulophidae), observed either in laboratory or in the field. The first behaviour concerns the contro! of
superparasitism of eggs. Females of Cirrospilus pictus (Nees) have been observed
in laboratory to kill the eggs previously laid by theirselves onto the host
Phyllocnistis citrella Stainton (Lepidoptera, Gracillariidae) using their ovipositor,
before proceeding to a new oviposition. Stinged eggs have also been found in the
field together with healthy eggs, so that it has been possible to attribute the same
strategy not only to C. pictus but also to Semielacher petiolatus (Girault) and
Citrostichus phyllocnistoides (Narayanan). Such a behaviour probably prevents in
the field eventual competition for resource, acting as a mean to contro! both
superparasitism and multiparasitism.
The second behaviour has been seen during the metamorphosis from the last instar
larva to pupa in C. pictus and Ratzeburgiola incompleta Boucek. In both species
the moulting has not been observed during the eonymph but at the end of the
pronymph phase, demarking then the prepupal phase from the pupal stage. The
cuticle of last instar larva, by appropriate sequence of shakes and tilting of the
body, is arranged in a sort of ligament connecting the Jast abdominal stemite to
the floor of the mine or to the meconium, permitting to the adult pharate stage
an easier emergence from the pupal skin.