The relation of parasite density of Microplitis rufiventris Kok. (Hym., Braconidae) to superparasitism and fate of its eggs

Abstract

The population of supernumerary parasite progeny of Microplitis rufiventris inside Spodoptera littoralis larvae was studied under different ratios of parasite‐host density. At constant population of host larvae and various levels of parasite density, the regression coefficient revealed that an increase of 0.78% in parasite eggs was found with the increase of every unit population of M. rufiventris. An inverse density‐dependent action of the latter was obtained under various density of S. littoralis larvae at constant population of the parasite. The regression coefficient indicates that for a unit increase in host density 0.06% fall in the number of parasite eggs/host larva was achived. A fraction of supernumerary parasite progeny was found to be eliminated during the egg‐stage. Elimination magnitude of the latter increased with the increase of supernumerary parasite population and vice versa Zusammenfassung Beziehungen zwischen Superparasitismus, Parasitendichte und Schicksal der Eier von Microplitis rufiventris Kok. in Spodoptera littoralis Boisd.‐Larven Es wurde die Population überzähliger Nachkommen von M. rufiventris in S. littoralis‐Larven bei verschiedenen Parasit/Wirt‐Dichterelationen untersucht. Bei konstanter Population von Wirtslarven und verschiedener Parasitendichte zeigt der Regressions‐Koeffizient, daß die Zunahme des Parasiten um eine Populations‐Einheit mit der Zunahme der Parasiteneier um 0,78% verbunden war. Bei verschiedener Wirtslarvendichte und konstanter Parasiten‐Population wurde eine umgekehrt dichteabhängige Aktion des Parasiten beobachtet. Der Regressions‐Koeffizient zeigte, daß mit der Zunahme der Wirtsdichte um eine Einheit die Zahl der Parasiteneier pro Wirtslarve um 0,06% abnahm. Ein Teil der überzähligen Parasitennachkommen wurde während des Eistadiums eliminiert. Der Umfang dieser Eliminierung stieg mit der Zunahme der überzähligen Parasiten und umgekehrt.

Functional response and mutual interference ofPeristenus spretus(Hymenoptera: Braconidae), a parasitoid ofApolygus lucorum(Heteroptera: Miridae)

“…Means in a column with the same letters are not significantly different (Tukey's HSD, SAS Institute, 1999 (Table 2). Consequently, higher parasitoid densities should be avoided when mass producing P. spretus, which agrees with many previous studies (Abe et al, 2005;Darrouzet et al, 2008;Hegazi et al, 1984;Hegazi & Khafagi, 2005).…”

“…If two or more eggs were laid on one host, competition between the larvae of solitary parasitoids results in all but one dying (Abe, Kamimura, & Shimada, 2005;Darrouzet, Boivin, & Chevrier, 2008;Hegazi, El-Minshawy, & Shaaban, 1984). In P. spretus, only one parasitoid developed per nymph, and supernumerary larvae were most likely killed by larval physical combat during the first instar.…”

Does superparasitism improve host suitability for parasitoid development? A case study in the Microplitis rufiventris-Spodoptera littoralis system

“…Probably the majority of parasitoid species develop solitary, which represents the ancestral life-history state (Mayhew 1998a;Ode and Rosenheim 1998), but the transition to gregariousness has occurred on many occasions (Mayhew 1998b). M. rufiventris is a solitary wasp that only one offspring develops per host (Hegazi et al 1984).…”

Effect of exposure time on mass‐rearing production of the olive fruit fly parasitoid, Psyttalia lounsburyi (Hymenoptera: Braconidae)

“…Hegazi et al. () also reported the influence of the parasitoid:host ratio on the superparasitism of Microplitis rufiventris Kok. (Hymenoptera: Braconidae).…”

“…Thus, manipulation of foraging time, that is exposure time, could reduce superparasitism and increase parasitoid emergence in a mass‐rearing programme. Superparasitism is a general pattern in many parasitoid species (Hegazi, El‐Minshawy, & Shaaban, ; Lawrence, ), but has not been studied in P. lounsburyi . A better understanding of the interplay between superparasitism and parasitoid emergence may also help improve mass rearing of P. lounsburyi .…”