Reproductive success and progeny sex ratio of a laboratory colony of Anagyrus fusciventris (Hymenoptera: Encyrtidae)

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.

KEYWORDS:

• Pseudococcus spp
• biological control
• laboratory rearing
• progeny sex ratio
• mating status

Acknowledgements

We thank our colleagues Asha Chhagan and Gonzalo Avila for their valuable comments on the earlier version of the paper, Amanda Hawthorne for providing sprouting potatoes for rearing mealybugs. We also thank the anonymous referees for suggestions to improve an earlier draft of this manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work is part of the Wine Research Programme of The New Zealand Institute for Plant and Food Research Limited (PFR), which is funded by the New Zealand Ministry of Business Innovation and Employment’s Strategic Science Investment Fund.