BIOLOGY OF TRICHOGRAMMA BREVICAPILLUM

Abstract

The biology of Trichogramma brevicapillum Pinto & Platner (Hymenoptera, Trichogrammatidae) reared on eggs of Trichoplusia ni (Hübner) (Lepidoptera), and the influence of some abiotic and biotic conditions on the parasitization strategy of the adults were studied. Egg, larva, prepupa, and pupa are described. Development of these stages lasted ca. 1,3, 1, and 5 days, respectively, at 25°. Reproduction is biparental, arrhenotokous. The preoviposition period lasts ca. 3 hr, and oviposition activity was maximal in the 3rd and 4th hr of the photophase and was minimal in the scotophase. The suitability of T. ni eggs as a host was maximal in the blastula stage of the embryo, decreased sharply in the early stages of differentiation, and increased rapidly in the later stages of embryological differentiation. A single ♀ reared from a host egg was larger and more fecund than 2 2 from eggs yielding 2 or 3 parasites. Oviposition by individual ♀♀ was restrained when the host egg density was limited, thus preventing superparasitization. The number of progeny per host egg and the ♂ proportion of the sex ratio were inversely related to the host egg density over a range of limited host densities. ZUSAMMENFASSUNG Die Biologie von Trichogramma brevicapillum Die Biologie von Trichogramma brevicapillum Pinto & Platner (gezüchtet auf Eiern von Trichoplusia ni (Hübner)) und der Einfluss einiger abiotischer und biotischer Faktoren auf die Parasitierungsstrategie der Adulttiere wurden studiert. Eier, Larven, Praepuppen und Puppen werden beschrieben. Die Entwicklung dieser Stadien bei 25° dauerte etwa 1, 3,1 und 5 Tage. Die Fortpflanzung ist bisexuell und parthenogenetisch‐arrhenotok. Die Praeovipositionsperiode dauerte etwa 3 Stunden. Die Eiablage war am grössten in der dritten und vierten Stunde der Photophase und am kleinsten in der Scotophase. Die T. ni‐ Eier eigneten sich am besten als Wirt im Blastulastadium des Embryos. Die Eignung nahm ab in den nächsten Stadien um in den späten Embryonalstadien wieder zu wachsen. Weibchen, die sich einzeln in einem Wirtset entwickelt hatten, waren wesentlich grosser und fruchtbarer als Weibchen aus Wirtseiern mit 2 und 3 Parasiten. Die Eiablage einzelner Weibchen wurde gehemmt, wenn die Dichte der Wirtseier begrenzt war; dies wirkt der Superparasitierung der Wirtseier entgegen. Die Nachkommenzahl pro Wirtsei und der männliche Anteil des Geschlechtsverhältnisses waren umgekehrt proportional zur Dichte der Wirtseier und zwar im Bereich begrenzter Dichte.

Development of Trichogramma australicurn Girault (Hymenoptera: Trichogrammatidae) on Helicoverpa armigera (Hubner) Eggs (Lepidoptera: Noctuidae)

“…However, the characteristics of the third "instar" mentioned by Saakian-Baranova (1991) are the same as the characteristics of the prepupal stage described by Flanders (1937), Pak and Oatman (1982) and Manweiler (1986).…”

“…The third "instar" has mandibles 18-22 pm long (Pak and Oatman 1982), or 22-24.4 pm long (Manweiler 1986). The fourth "instar" has mandibles 21-28 pm long (Pak and Oatman 1982). Manweiler (1986) did not identify a fourth larval "instar" in the development of T. minutum and T. platneri.…”

“…Further, the number of larval instars of Trichogramma species from studies appears variable (e.g. Flanders 1937;Pak and Oatman 1982;Manweiler 1986;Saakian-Baranova 1991). These kinds of information are important for comparison between development a n d growth of Trichogramma in an insect host egg and an artificial diet, and will provide insight into nutritionally-induced abnormalities.…”

Effect of Wolbachia on the Survival and Reproduction of Trichogramma kaykai Pinto & Stouthamer (Hymenoptera: Trichogrammatidae)

“…Trichoplusia ni Hübner (Lepidoptera: Noctuidae) eggs were obtained from a colony maintained at the University of California, Riverside, on an artificial diet developed by Shorey & Hale (1965) and modified by Pak & Oatman (1982). T. ni laid their eggs on paper toweling that lined the inside of an oviposition unit (Knott et al 1966).…”

Effect of host availability and egg load in Trichogramma platneri Nagarkatti (Hymenoptera: Trichogrammatidae) and its consequences on progeny quality

“…However, the decision of whether or not to parasitize a host depends on the number of mature eggs in the female's ovaries and her age (Donaldson and Walter, 1988;Trudeau and Gordon, 1989;Minkenberg et al, 1992;Godfray, 1994). Species of Trichogramma (Hymenoptera: Trichogrammatidae) have been considered proovigenic (Pak and Oatman, 1982) and if hosts are abundant, nearly all of their eggs are laid in the first few days of life (Pak et al, 1985, Hohmann et al, 1988Fleury and Bouletreau, 1993). Pak et al (1985), however, speculated that under host scarcity conditions, females might be able to continue searching over an extended period of time by controlling the ovulation and ovisorption processes.…”