Abstract
ABSTRACT The effect of different initial numbers of the host, Rhopalosiphum maidis, on the demographic statistics of its parasitoid, Lysiphlebus delhiensis (Subba Rao & Sharma), was determined under constant laboratory conditions. The survival rate (lx) of the female parasitoid was unaffected by host density, with an average adult life-span of 7.2 days at 20 ± 1°C. The age specific fecundity rate (mx) was host density-dependent. The value of mx decreased rapidly from the first day of oviposition until the death of the female. Fecundity was highest with an average of 270.8 ± 35.9 SD mummies/female at 200 hosts/cage (30 × 30 × 45 cm); the maximum number of mummies yielded by any female was 304. The relationship between host density and the number of aphids parasitised per female was linear at ≤50 aphids/cage/day but at higher host densities (≥ 100 aphids/cage/day) a significant curvilinear regression was observed. The intrinsic rate of natural increase (rm) increased with increasing host density. Maximum va...
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