Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Intraspecific larval competition in two solitary parasitoids, Apoanagyrus (Epidinocarsis) lopezi and Leptomastix dactylopii.

Abstract

The encyrtids Apoanagyrus lopezi and Leptomastix dactylopii are strictly solitary endoparasitoids of larvae and adults of the pseudococcids Phenacoccus manihoti and Planococcus citri, resp. For both species, the survival rate of the supernumerary parasitoid according to the time interval between the two ovipositions has been determined by dissecting superparasitized hosts. For A. lopezi, the survival rate of the second parasitoid is at least equal to 30% when the time interval between the two ovipositions is less than 2 days, then it drops rapidly down to 10%. For L. dactylopii, the survival rate of the second parasitoid is 23% for a 1-h interval between the two ovipositions and thereafter decreases very rapidly to reach a stable value of 7%. Differences between the two species might be partly due to the immunological defence reactions of their respective hosts. In the two Encyrtidae, supernumerary individuals are eliminated partly by physical attack between larvae in the 2nd instar and partly by a physiological suppression of the second parasitoid by the first in the egg or larval stage. Earlier findings had shown that females of each species oviposit preferentially in hosts in which their progeny has the highest probability of survival: this would indicate that the adaptive value of conspecific superparasitism depends essentially on the survival rate of the second parasitoid in superparasitized hosts.