ABSTRACT

Anagyrus fusciventris (Girault) is a parasitoid of both Pseudococcus calceolariae (Maskell) and P. longispinus (Targioni Tozzetti), two economically important mealybug pests in New Zealand. A male-biased sex ratio was often observed in a laboratory colony of A. fusciventris. We investigated the effect of mating status on female A. fusciventris longevity, fecundity, progeny sex ratio and the rate of parasitism achieved under controlled laboratory conditions. In addition, the impact of host body size on progeny sex ratio was investigated. The progeny sex ratio of unmated (virgin) females (VF) and two types of mated females (24hM: opportunities for mating limited to 24 h or LtM – lifetime opportunities for mating) was tested under similar conditions. Results indicated that females can be reproductively active within 24 h. On average, 24hM females produced 23% female offspring while LtM females produced 45% females, suggesting that multiple mating is required for a balanced sex ratio. VF produced only male offspring through arrhenotokous parthenogenesis. When reared at 23°C and 16 h photoperiod, VF, 24hM and LtM females lived for 25, 44, 51 days, and parasitised 46, 67 and 87 mealybugs respectively. The average lifetime reproductive output (total number of offspring emerged) of VF, 24hM and LtM females was 41, 58 and 75 offspring, respectively. Female-biased progeny emerged from larger hosts while male-biased progeny often emerged from smaller hosts. Implications of these results are discussed in relation to opportunities to improve the quality of a laboratory colony with a balanced progeny sex ratio.

摘要

Angyrus fusciventris (Girault) 是Pseudococcus calceolariae (Maskell) 和P. longispinus (Targioni Tozzetti) 的寄生物，这两种粉蚧在新西兰具有重要的经济意义。在A. fusciventris的实验室群体中经常观察到偏向男性的性别比例。我们研究了交配状态对雌性A. fusciventris 的影响在受控实验室条件下实现的寿命、繁殖力、后代性别比和寄生率。此外，研究了宿主体型对后代性别比的影响。在类似条件下测试了未交配（处女）雌性 (VF) 和两种类型的交配雌性（24hM：交配机会仅限于 24 小时或 LtM - 终生交配机会）的后代性别比。结果表明，雌性可以在 24 小时内进行生殖活跃。平均而言，24hM 雌性产生了 23% 的雌性后代，而 LtM 雌性产生了 45% 的雌性，这表明平衡的性别比例需要多次交配。VF 通过 arrenotokous 孤雌生殖仅产生雄性后代。在 23°C 和 16 小时光照条件下饲养时，VF、24hM 和 LtM 雌性可存活 25、44、51 天，寄生 46 天，分别为 67 和 87 粉蚧。VF、24hM 和 LtM 雌性的平均终生繁殖产量（出现的后代总数）分别为 41、58 和 75 个后代。偏向雌性的后代来自较大的宿主，而偏向雄性的后代通常来自较小的宿主。讨论了这些结果的影响，以提高具有平衡后代性别比的实验室群体质量的机会。