Entomological Science (2013) 16, 54-59

Seyed Mohammad Tabadkani, Ahmad Ashouri, Vahid Rahimi-Alangi and Mehdi Fathi-Moghaddam (2013)
When to estimate sex ratio in natural populations of insects? A study on sex ratio variations of gall midges within a generation
Entomological Science 16 (1), 54-59
Abstract: Precise estimation of arthropods' sex ratio is an important issue in a wide range of ecological studies and biological control programs. Although, in many cases changes in arthropods' sex ratio may be under the control of parents or some symbiotic microorganisms, biased sex ratios in some other species are caused by some extrinsic factors, neglect of which may lead to under/overestimation of true sex ratio. In this paper, we pursued those factors that cause false estimation of sex ratio in insects' species. We studied the predatory gall midge, Aphidoletes aphidimyza Rondani (Diptera: Cecidomyiidae), an important biological control agent of aphids, that shows protandry (i.e. early male emergence), differential lifespan of sexes, and differential distribution of sexes across habitat. Ten populations of A. aphidimyza were released separately in transparent cages and their sex ratio variations were recorded every 12 hours. The primary sex ratio in this species seems to be slightly male-biased (52.41% males), however early emergence of males biases the sex ratio up to 72% males in a few hours after emergence. Shortly after the emergence of females, the sex ratio reaches its primary situation, but as a result of male-biased mortality after mating, the proportion of females increases gradually to 97% by the fourth and fifth days after emergence. These results explicitly suggest that direct estimation of sex ratio in natural populations may be affected by some secondary factors such as differential mortality of sexes, protandry, and differential distribution of males and females over time and/or across habitat.
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Link to article at publishers website
Database assignments for author(s): Ahmad Ashouri

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
population dynamics/epizootiology

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Aphis gossypii	Cotton (Gossypium)	Iran
	Acyrthosiphon pisum		Iran
Aphidoletes aphidimyza (predator)	Aphis gossypii	Cotton (Gossypium)	Iran
Aphidoletes aphidimyza (predator)	Acyrthosiphon pisum	Broad/faba bean (Vicia faba)