Efeito da densidade de Nasonia vitripennis (Walker, 1836) (Hymenoptera: Pteromalidae) e do hospedeiro Chrysomya megacephala (Fabricius, 1794) (Diptera: Calliphoridae) sobre os aspectos biológicos do microhimenóptero / Effect of the density of Nasonia vitripennis (Walker, 1836) (Hymenoptera: Pteromalidae) and Chrysomya megacephala host (Fabricius, 1794) (Diptera: Calliphoridae) on the biological aspects of the microhymenoptera

Renata da Silva Mello

The present study aimed to evaluate reproductive aspects of Nasonia vitripennis (Walker, 1836) reared in pupa of Chrysomya megacephala (Fabricius, 1974) under controlled environmental conditions (Temperature= 27C on day/ 25C at night, 7010 humidity relative, 14 hours fotofase). It was observed the post-embryonic development, the productivity of parasitoids emerged by pupa, the rate of parasitism, the sexual ratio and the longevity of the parasitoids females in function of the use of different densities of parasitoids for host (1: 1, 3:1, 5:1, 7:1, 9:1, 11:1), different densities of hosts (1: 1, 1:2, 1:3, 1:4 and 1:5), both displayed to the parasitism for 48 hours, and different times of exposure of a host to one parasitoid for 24, 48, 72 and 96 hours. Pupaes had been displayed to nulliparous females in test tubes covered with hidrophobic cotton, following the described relations above, to follow the pupaes was individualized until an appearancy of adults dipterous or parasitoids. Lots of host pupae not exposed to parasitism and receiving the same experimental treatment, were used as control. Each treatment was constituted by 20 repetitions. It was used analyzes of variance with 5% level of significance for statistic inferences. It was observed a trend to the extend of the average time of post-embryonic development in function of the increase of the densities of parasitoids and the densities of hosts. The use of five parasitoids for host presented the highest productivity of parasitoids in relation to the other tested densities and from this the reduction of emerged the total number of parasitoids, especially of females and an increase in the percentage of males was observed, possibly for effect of the superparasitism. The same was verified with the addition of hosts, where was observed a higher productivity using a parasitoid per host and a lesser productivity using one parasitoid: three hosts. It also had a shunting line of the sexual reason for females, however, the increase of hosts was not verified increase in agreement percentage of males. Regarding the use of different times of exposure of the host to the parasitism presented the biggest times of postembryonic development with the exposition for 72 hours for the females and the emerged total of parasitoids, the other times of exposition had not presented significant difference between itself. The average productivity of parasitoids did not vary for the use of different times of exposure however, it had a trend to the increase of the rate of pupaes impracticable with the increase of the exposition time, possibly for the deleterious effect of pupaes for the exploration of the females parasitoids. In the same way it had an increase in the percentage of pupas impracticable in function of the increase of the density of parasitoidss and pupaes with appearancy of dipterous in function of the increase of used hosts. The parasitsm rate, however, it was little influenced by the increase of the density of parasitoids and for the different times of exposure.

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