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What is “Sexual size dimorphism”?

Sexual dimorphism refers to physical differences between males and females of the same species. One such difference can be in size, and we have a great example of this in Hong Kong with our very own Great Golden Orb Weaver Spider.

So, when you look into those large spun webs across the forest paths and trees, and you see the big spider, that is in fact a female, which can be much, much bigger - maybe up to 10 times - larger than the male. The male here is the much smaller red coloured spider, at the corner of the web.

The larger size female is typically thought to be selected through fecundity selection, which has as its base the idea that bigger females can produce more eggs, thus more offspring.

This little male will try to mate at the central hub of the web, slowly traversing the web, trying not to get eaten, and when reaching the hub, mounts the female. You can find many males around one large female, as their odds of survival are not great.

In one similar orb-web spider species that was studied a male survives his first copulation depending on the duration of the genital contact: males that jump off early (before 5 seconds) have a chance of surviving, while males that copulate longer (greater than 10 seconds) invariably die. Prolonged copulation, although associated with cannibalism, enhances sperm transfer and relative paternity. So, you make your choice, and take the consequences.

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