The developmental strategy of an idiobiont ectoparasitoid, Dendrocerus carpenteri  : influence of variations in host quality on offspring growth and fitness

Abstract

Dendrocerus carpenteri (Curtis) (Hymenoptera: Megaspilidae) is a solitary hyperparasitoid, which attacks prepupal and pupal stages of hymenopteran parasitoids inside mummified aphids. The larva feeds externally on the host, which is envenomed by the female at oviposition. To evaluate the influence of variations in host quality on the growth, development and fitness of D. carpenteri, we varied the size and developmental stage of the primary parasitoid host (Aphidius ervi Haliday), which was reared on different instars of pea aphid [Acyrthosiphon pisum (Harris)] and English grain aphid [Sitobion avenae (F.)]. Within each kind of host, females eclosed from the relatively larger mummies, while males eclosed from the smaller mummies. Host size and hyperparasitoid size were correlated, and females were larger than males. In hyperparasitoids developing on prepupal and pupal hosts, development time from oviposition to adult eclosion was proportional to size; females required more time for development than males. The mean relative growth rate was the same in males and females and increased with host quality, as predicted by the growth model of Mackauer and Sequeira (1993) for idiobiont parasitoids. Larvae developing on late-pupal stages and pharate adults of A. ervi were unable to consume sclerotized host tissues; they were smaller and needed more time for development. The average number of mature eggs at eclosion was six, except in females developing on suboptimal hosts, which contained only one egg or none. Egg volume was correlated with female size, possibly reflecting differences in larval ontogeny. We provide equations describing the relationship between host quality as indexed by hind-tibia length of the mummified aphid and adult body size in terms of dry mass, development time and mean relative growth rate of D. carpenteri. We discuss the usefulness of host size as a proxy of host quality for idiobiont parasitoids, and provide examples of exceptions.

Life history correlates and reproductive biology of Laelius pedatus (Hymenoptera: Bethylidae) in The Netherlands

“…Our results are consistent with this model, as are other studies on idiobiont ectoparasitoids (e.g. Harvey et al, 1998;Otto & Mackauer, 1998). Koinobionts attack hosts which continue to develop, and a range of developmental strategies may occur, so that similar trends to idiobionts may be observed, or development rate may increase in larger hosts so that development time is constant (see Sequeira & Mackauer, 1992;Harvey et al, 1994;Mayhew & van Alphen, 1999).…”

“…A few other intraspecific studies of parasitoids show a positive correlation between body size and egg size (e.g. O'Neil & Skinner, 1990;Visser, 1994;Otto & Mackauer, 1998). Like many other idiobiont ectoparasitoids (Flan ders, 1942;Mayhew & Blackburn, 1999), L. pedatus lays anhydropic eggs (see Jervis & Kidd, 1986), which are large, and yolky with a thick chorion.…”

Remarkable similarity in body mass of a secondary hyperparasitoid Lysibia nana and its primary parasitoid host Cotesia glomerata emerging from cocoons of comparable size

“…Comprehensive studies examining the combined effects of host size and age on the development of pupal parasitoids are scarce, and, in particular, hyperparasitoids have been largely ignored (but see Otto and Mackauer, 1998). Furthermore, little is known about the importance of hyperparasitoids in natural communities, or in agroecosystems (Sullivan and Völkl, 1999;Brodeur, 2000).…”

Host characteristics related to host use by the flesh fly, Blaesoxipha japonensis (Diptera: Sarcophagidae), a parasitoid of adult grasshoppers

“…Whereas most parasitoids use sedentary insects such as scales or confined stages of insects, such as eggs, larvae, or pupae, as their hosts, only a small percentage use the active stages, such as adults, as their hosts (Quicke, 1997;Otto and Mackauer, 1998;Stireman et al, 2006). Some parasitoid flies use adults of orthopteran insects such as grasshoppers or crickets as their hosts (Greathead, 1963;Cade, 1975;Shima, 1999).…”