Comparative life table, behavior and competition studies of trichogramma brevicapillum and t. pretiosum
1982
PAK, G.A. | OATMAN, E.R.
Life-table studies of Trichogramma brevicapillum Pinto & Platner and Trichogramma pretiosum Riley were conducted at various fluctuating temperatures (means ± 5°), from 15 to 35°. The intrinsic rate of natural increase (r) was higher for T. brevicapillum than that for T. pretiosum at 30 and 35°, and was higher for T. pretiosum between 15 and 25°, due to differences between the 2 spp. in development, longevity, fecundity, sex ratio, and number of progeny per host egg. T. brevicapillum had a higher fecundity than T. pretiosum, but its development was slower (ca. 10%), and was retarded facultatively at temperatures of 20° and below, probably due to diapause. Ovipositional behavior of T. brevicapillum and T. pretiosum was similar, but differed in the duration of the different ovipostional activities. Superparasitization occurred by both species when the host egg supply was limited and exposed to more than 1 female simultaneously. T. pretiosum laid more eggs per host egg than T. brevicapillum at various parasite densities. When eggs were exposed to both species simultaneously, oviposition was intermediate between the number of eggs laid by each species separately. From such eggs, 24 and 76% of the emerged progeny was T. brevicapillum and T. pretiosum, respectively, and these percentages were independent of parasite density. The results may explain the distribution of T. brevicapillum and T. pretiosum in California, and may assess their fitness for mass-release and establishment attempts.
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