Influence of host age and host deprivation on longevity, egg load dynamics and oviposition rate in Microplitis rufiventris

Abstract

AbstractAdult size, longevity, egg load dynamics and oviposition of Microplitis rufiventris Kok. which began their development in the first, second, third (preferred hosts) or fourth (non‐preferred hosts) instar larvae of Spodoptera littoralis (Boisd.) were studied. The parasitoid size was largely determined by the initial host size at parasitism. Non‐ovipositing females derived from older hosts lived for longer periods than those derived from younger ones. However, the ovipositing females, irrespective of their size, lived for almost the same periods. At emergence, the oviducts of adult females contain a significant amount of mature eggs available for oviposition for a few hours on eclosion day. Egg load increases during the early phase of adult life. The amount of additional mature eggs and rate of egg maturation per hour was greater for wasps derived from preferred hosts compared with those in females derived from non‐preferred hosts. The pattern of egg production in M. rufiventris females depended on the availability of hosts for parasitization. Host‐deprived females depleted the egg complement with aging; the longer the host deprivation, the lower the oviduct egg load. Marked reduction in both realized or potential fecundity of host‐deprived females was observed following host availability. Host privation for more than 3 days induced a marked deficit fecundity pattern through the female's life. The realized fecundity was determined by the interaction among host availability, the number of eggs that are matured over the female's life span, oviposition rate and host size from which the female was derived. These results suggest that: (i) M. rufiventris wasp is a weak synovigenic species; (ii) the maturation of additional eggs is inhibited once the maximum oviduct egg load is reached; (iii) the egg load of the newly emerged female is significantly less than the realized fecundity; and (iv) because M.rufiventris females oviposit fewer eggs when they begin depleting their egg supply at 3 days, augmentative releases will require release immediately following emergence to ensure the highest parasitization rate in the field.