Abstract

The solitary endoparasitoid, Microplitis rufiventris is considered one of the principal wasps on the cotton leaf moth, Spodoptera littoralis larvae. It has a strange sort of obligate diapause. The data present an evidence of persistent low-level diapause throughout the year and every year that observed under mass rearing conditions. When continuous rearing was done throughout the year at 25°C and 12/12 h L/D, a small portion of the individuals in each large samples of each generation entered diapause. So, a long-timed experiment that repeated three years and collecting dataset that required regular extensive dissections and microscopic observations of emerged diapausing wasps was carried out. This diapause spontaneously terminates after time periods similar each year, showing an evidence of “time memory” in diapausing wasp behavior. The duration of this time period is taken as a proxy of diapause intensity. This had occurred whether the large number of individuals originated in summer from field-collected host larvae or from three successive years of laboratory-rearing parasitoids. Contrary to non diapausing wasps, diapausing females emerge some days early than males. This is the first report of new sort of obligate diapause in diapause induction and termination in M. rufiventris under the same constant rearing conditions. Fecundity of diapaused wasps was diapause intensity dependent. Wasps diapaused for 60-86 days (long diapause) have more number of mature eggs than either of those diapausing for short period (23-57 days) or those of longer diapause (90-165).

Key words: Microplitis rufiventris, mass rearing conditions, obligate diapause, diapause intensity, generation effect, fecundity.