  In Chile and Uruguay,the gregarious Pteromalidae (Monoksa dorsiplana) has
been discovered emerging from seeds of the persistent pods of Acacia caven
attacked by the univoltin bruchid Pseudopachymeria spinipes. We investigated
the potential for mass rearing of this gregarious ectoparasitoid on an
alternative bruchid host, Callosobruchus maculatus, to use it against the
bruchidae of native and cultured species of Leguminosea seeds in South America.
The mass rearing of M.dorsiplana was carried out in a population cage where the
density of egg-laying females per infested seed was increased from 1:1 on the
first day to 5:1 on the last (fifth) day. Under these experimental conditions
egg-clutch size per host increased, and at the same time the mortality of eggs
laid also increased. The density of egg-laying females influenced the sex ratio
which tended towards a balance of sons and daughters,in contrast to the sex
ratio of a single egg-laying female per host (1 son to 7 daughters). The mean
weight of adults emerging from a parasitized host was negatively correlated
with the egg-clutch size, i.e., as egg-clutch size increased, adult weight
decreased. All these results show that mass rearing of the gregarious
ectoparasitoid M.dorsiplana was possible under laboratory conditions on an
alternative bruchid host C.maculatus. As M.dorsiplana is a natural enemy of
larval and pupal stages of bruchidae, the next step was to investigate whether
the biological control of bruchid C.maculatus was possible in an experimental
structure of stored beans.
