Hairy crabs are the great autumn delicacy of eastern China, and an obsession for those who can afford to eat them. The female crabs ripen in the ninth lunar month, the males in the tenth, and from then until the end of the year they are almost inescapable.

A pair of crabs crouched on my plate, eyeballing each other like adversaries, their legs spiky with yellow hair.

The male was big and beefy, the colour of a mandarin, with claws bedded in dark mossy fur. The female was smaller, its shell a less flamboyant shade of orange.

Steam drifted up from both of them. I took a deep breath and prepared for the attack.

Eating hairy crabs is a wild and messy business. You must pull off the legs and claws, prise open the shells and scrape, pick, suck and crunch until you have extracted every last, delicious morsel.

The pale, silken flesh of the crab legs is delectable enough, but their shells contain the real treasures: the golden, voluptuous semen of the males and the bright orange roe of the females, sprawled lazily atop a custardy mess of meat.

From Our Own Correspondent Insight and analysis from BBC correspondents, journalists and writers from around the world

Broadcast on Radio 4 and BBC World Service Listen to the programme Download the programme

Of course, for those who find eating whole crabs a hassle, restaurants offer seasonal menus of dishes made with meat that has been painstakingly excavated from the shells.

You might try the legs stir-fried with asparagus, the luscious shell-meat and roe on a dishful of quivering tofu, or a hairy crab version of Shanghai's most famous steamed dumpling, the xiao long bao.

The crabs have long inspired passion in their devotees. The 17th Century playwright Li Yu wrote that his heart lusted after them, and there was not a day in his life when he had not thought of them.

I had not intended to eat hairy crab every day during my recent stay in Shanghai, but they seemed to greet me everywhere I went.

The crab's heart is a sinister grey flap of rubbery flesh, smaller than a SIM card, and should never be eaten

And although I had always considered myself to be a competent crab-picker, I found myself taking what seemed to be an advanced course in the art of crab-eating, because everyone I met offered me a new piece of advice.

My friend Jason's mother told me to leave two legs attached to each half of the body like a handle, so I could raise it to my lips and chomp out the strandy white flesh at the sides.

The uncle of another friend, Rose, taught me how to stick parts of both claws together so they looked like a butterfly.

And most intriguingly, he showed me how to turn the stomach inside out to reveal a tiny knobbly appendage that resembled the head of an ancient monk, complete with wizened face and long, straggly beard.

There was plenty of medical advice too, because eating hairy crabs is a dangerous game, as any Shanghainese can tell you.

According to Chinese medicine, their flesh is perilously cold, and must be balanced with warming foods, which is why they are always served with vinegar and ginger, and sometimes a flask of Shaoxing rice wine.

And crabs should never be eaten with "cold" persimmon, because it is thought to be a toxic combination.

Then there are the parts of the crab that must be avoided. The pillowy, finger-like lungs and plasticky pyramid of the stomach should be discarded, said another friend, Haichen.

Image caption During the autumn, hairy crabs are widely sold at markets in eastern China

And do not, whatever you do, eat the heart, she added - it is a sinister grey flap of rubbery flesh tucked away inside the body, which is even colder than the meat and should never be eaten. Smaller than a SIM card, it is easily overlooked.

After a couple of weeks of excessive crab-eating, despite my delight, I was becoming paranoid.

Haichen had warned me that for women especially, crabs should be eaten in extreme moderation, but I could not seem to escape them.

A friend's uncle taught me how to stick parts of both claws together so they looked like a butterfly

I was ambushed by crabs at what was supposed to be simple lunches at the homes of friends, surprised by crab dishes on every dinner table.

Even after a wine-and-food pairing event when I had been tasting crab all day long, the piece de resistance at the judges' banquet was... crabmeat on a bed of eggwhite custard.

Despite my diligent consumption of ginger and wine, would I succumb to the symptoms of cold - stomach-ache and vomiting?

And just how soon after eating a crab was it safe to consume persimmons, which were also perfectly in season and quite irresistible?

I recalled, with a shudder, that I must have eaten a few of the flabby grey hearts before I had learned to pick them out.

For a few days I walked around in a state of unease, waiting for the crabs' revenge. But I am pleased to report that I survived the experience in robust good health.

And I cannot wait to go to Shanghai next autumn for more.

How to listen to From Our Own Correspondent:

BBC Radio 4: Saturdays at 11:30 and some Thursdays at 11:00.

Listen online or download the podcast.

BBC World Service: Short editions Monday-Friday - see World Service programme schedule.

You can follow the Magazine on Twitter and on Facebook