OBSERVATIONS ON THE FECUNDITY OF HYSSOPUS THYMUS (HYMENOPTERA: EULOPHIDAE)

Abstract

AbstractThe fecundity of Hyssopus thymus Girault females does not normally vary between generations within a single year, but differences frequently occur between years. A weighted mean annual fecundity of 14 eggs per female under laboratory conditions has been determined by pooling several years’ records, although the maximum number of eggs laid by a female was 130. A mean of 20 eggs per female was determined under quasinatural conditions. The weight of the host, Rhyacionia buoliana (Schiffermüller) (Lepidoptera: Olethreutidae), limits the number of eggs laid per host during the early spring when shoot moth larvae are small. When the host larvae are larger, size is no longer a limiting factor in the number of eggs deposited per host. There is a preoviposition period of about 3 days and egg production is synovigenic. The number of fully developed eggs within a female at one time varies between about 7 and 12 eggs on a 3-day cycle, and never exceeds 16. Each female wasp attacks two or three large host larvae and this number is probably doubled when the host larvae available for attack are small.