Sting frequency and progeny production of lab-cultured Cotesia marginiventris

Abstract

A laboratory experiment was conducted to determine the impact of sting frequency on progeny production of Cotesia marginiventris (Cresson) (Hymenoptera: Braconidae), a solitary, koinobiont endoparasitoid of noctuid pests. In replicated trials, young, mated, host-deprived C. marginiventris females were exposed to three Spodoptera exigua (Hü bner) (Lepidoptera: Noctuidae) early instar larvae, one at a time, in Petri dish arenas, and observed as they stung these hosts once, twice, or thrice. The average amount of time that elapsed between stinging a host ranged from a minimum of 3 min, when females were exposed to unstung hosts, to a maximum of 8-11 min when females were exposed to previously stung hosts. Sting frequency had no effect on the yield of C. marginiventris progeny; approximately 90% of hosts, in all treatment groups, yielded a parasitoid mature larva, which spun a cocoon. No hosts yielded more than one parasitoid. The percentage of adult female progeny tended to increase with sting frequency; hosts that were stung thrice yielded 60% female C. marginiventris adults. The production of female progeny may depend on the egg allocation pattern of C. marginiventris females as well as the competitive interactions between siblings developing inside a shared host. This study suggests that S. exigua larvae can sustain 2-3 stings without diminishing their ability to yield a C. marginiventris mature larva. Provisioning enclosures with enough hosts to exceed the daily (per capita) oviposition rate of C. marginiventris females might limit the repeated stinging of the same hosts.

Densidade de fêmeas de Trichospilus diatraeae (Hymenoptera: Eulophidae) por pupa de Diatraea saccharalis (Lepidoptera: Crambidae)

“…A progênie pode variar conforme a espécie hospedeira, como ocorreu com T. diatraeae emergidos de pupas de Thyrinteina arnobia, Hylesia paulex (Pastori et al 2012a) e Spodoptera cosmioides Walker, 1858 (Lepidoptera: Noctuidae) (Zaché et al 2012). Além disso, a produção de progênie pode depender do grau de competição entre irmãos em desenvolvimento dentro de um hospedeiro compartilhado (Riddick 2008), resultando em menor tamanho corporal (Fidgen et al 2000). A progênie produzida por cada fêmea de T. diatraeae nas pupas de D. saccharalis diminuiu o número de indivíduos à medida que aumentou a densidade desse parasitoide.…”