Superparasitismo y competencia intraespecífica entre larvas del parasitoide Trichopoda giacomellii (Blanchard) (Díptera: Tachinidae)
Abstract
Intraspecific competition among parasitoid larvae of Trichopoda giacomellii (Blanchard) was studied underfield conditions. Parasitized adult hosts, Nezara viridula (L.), were collected during November 1986 - February 1987 in the experimental field of the Faculty of Agronomy of La Plata, and kept in captivity until death. Every host (n= 660) was then dissected, and the initial number of larvae/ host computed. The mean number of parasitoids/host that reached adult stage and the mean pupal length were calculated. The maximum number of adult parasitoid/host was 2 (4.02 % of all cases) while 1 adult parasitoid/host was found in 66.04% of hosts. No pupae was obtained from the remaining hosts. Regression analysis indicated that an increase in the initial larval density from 1 to 20, caused a reduction in survivorship of about 45%. These results suggest a contest-like larval competition, where a mean number of 0. 762 survivors/host and a mean pupal length of 8.25 mm were obtained independently of the initial number of larvae/host. Furthermore, observations of lacerated small larvae and dead larvae at or near the point of entrance into the host without signs of attack, suggest cannibalism and/or allelopathy as mechanisms used by dominant larvae to eliminate competitors.
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