Influência coespecífico e da densidade de hospedeiros na progênie de fêmeas de Diachasmimorpha longicaudata

Abstract

This work aimed to evaluate the influence of conspecific and density of host in offspring of Diachasmimorpha longicaudata female. Initially we aimed to evaluate the optimal density of D. longicaudata females and larvae of C. capitata and identify the influence of a conspecific in the females production and the intensity of parasitism. Females of the parasitoid and host larvae were obtained from rearing stock maintained in the laboratory of biological control of the UNIMONTES. In each cage were placed one, two and three females of the parasitoid and three densities of C. capitata larvae of third instar (10, 20 and 30) exposed to parasitoids in "units of parasitism" for one hour. The number of scars on pupae was recorded. The pupae were classified as unparasitized (no scar), parasitized (presence of one scar) and superparasitized (presence of more than one scar). After emergence, adults were sexed and quantified. The intensity of parasitism was assessed by means of proportion of non-parasitized larvae, parasitized larvae and superparasitized ones from those offered to parasitism. A parasitoid sex ratio was calculated by the formula: females / (males + females). It was noted that when females are isolated, the intensity of parasitism was lower. The production of female in the offspring was stimulated by the presence of conspecific in the same environment. In the ratio 1/10 (female and larva), the sex ratio in superparasitized larvae was greater when there were three females in the cage. The second part of the study aimed to evaluate the preference of D. longicaudata female for C. capitata larvae parasitized or unparasitized. For this, the third instar larvae previously parasitized or unparasitized were offered to females in "units of parasitism", by means of free choice and no choice tests. Each cage had one or two female parasitoid. A proportion of 10 larvae / female in either situation was supplied. "Units of parasitism" remained in their cages for two hours. In the free choice test, we verified the ability of discrimination of the females in relation to parasitized or unparasitized larvae. Two observations of the behavior of females in relation to "units of parasitism were made: visit without oviposition and visit with oviposition. The preference for the host was verified by the number of times the female made ​​the landing without oviposition and oviposition in the "units of parasitism". The intensity of parasitism in parasitized and unparasitized larvae and the offspring sex ratio were evaluated. D. longicaudata females preferred unparasitized larvae for oviposition. There was a greater proportion of superparasitized larvae, and from these greater amount of females was obtained. D. longicaudata females can discriminate parasitized from unparasitized larvae. Superparasitism is a characteristic of this species, and result in biased progeny for females.