Morphology and Biology of Trichogrammatoidea bactrae (Hymenoptera: Trichogrammatidae), Imported from Australia as a Parasitoid of Pink Bollworm (Lepidoptera: Gelechiidae) Eggs

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Abstract
Morphological and selected biological studies are described for Trichogrammatoidea bactrae Nagaraja, recently imported into the United States from Australia as an egg parasitoid of the pink bollworm, Pectinophora gossypiella (Saunders). Females maintained at 24°C averaged 23.2 ± 6.3 (SD) eggs per ovary. Unlike many Trichogramma species that apparently have four larval instars, T. bactrae develops through only two instars. Larvae also lack well-defined primary segmentation, which suggests that they are relatively immobile. The characteristic blackening of the vitelline membrane of the host egg occurs during the prepupal stage. Measurements and scanning electron micrographs of all T. bactrae immature stages are described. T. bactrae development, mortality, and adult fecundity and longevity were examined at several constant temperatures in the laboratory. Host age suitability studies were done at 25°C. Across all temperatures tested (15-32.5°C), the majority (ݲ = 83.7%) of T. bactrae emerged between 0700-1000 hours, and the sex ratio (progeny from mated females) was predominately female (ݲ = 64.9%). Virgin females exclusively produced males. Immature mortality ranged from 10.6 to 34.6% between 15 and 30°C; however, at 32.5°C mortality was 73%. T. bactrae preferred to oviposit in white eggs (<24 h old) versus older eggs and produced an average of 20.72 immatures/female (95% CI = 17.7 to 23.7). Regardless of rearing temperature, T. bactrae females completed oviposition within the first day of emergence and usually died within 1.18 ± 0.048 (ݲ ± SE) days. Males never lived longer than one day. Potential for T. bactrae to become established in cotton in the southwestern United States is discussed.