It is the age when curiosity grows wings, knees bleed and a lad realises he can easily out-sprint his old dad.

Joe-Joe, eight on June 18, decided to be Zorro, and we went to the village to pick up Buzz Lightyear, Rambo and Spiderman. Little Red Riding Hood, Woody the cowboy and two more superheroes were driven to the pool party by their mums.

There were no bookings for the holiday cottage, so a vague suggestion that we might invite a few pickles round for a swim swiftly ballooned into a riotous splash.

I hid from the hosepipe fight and observed the glee. High School Musical was belting out of the CD player but could barely be heard above the racket, and between long contented smiles and sighs I chewed on the conundrums of privilege, influences and what makes for the indelible memory of childhood.

Hollywood has a lot to answer for, yet it seriously lost the day; far too shallow. Within minutes the costumes were gone, trunks were on and the simple element of water play endured as it has and
will forever.

And by the time the farm was bathed in the sweet light of sunset, Joe Joe, his pal Juan and I were wandering through the freshly-weeded top vineyard skimming the grass borders in search of another kingdom. Our present to our son was an insect net and magnifying glass, while aunts and uncles sent guidebooks and a science box in which to keep his bits, bobs and bugs.

Joe-Joe is a jam jar lad – aren't they all at heart? – occasionally asking me to punch air holes into lids. Fantastic. Bug hunting is rocket fuel for young minds, gets them into the real world and is easy, free, fascinating and fundamental. Do you have the faintest idea, for example, how many kinds of beetle there are? Have a stab. When I was asked, I suggested between four or five hundred, which struck me as a little bold. The answer is about 350,000, or rather that's just the small number humans have identified. The total could be 20 times more.

"The insect world is another galaxy, an amazing kingdom we barely know." That is how retired scientist Joe Maddox tells it in his soft Alabama sing-song voice, eyes bright, a half smile on his lips. He stayed in our cottage for a fortnight with his wife Janice, fellow entomologist and ex-University of Illinois colleague Mike Irwin and his wife Bonnie.

"You know, humans have identified about a million insects, but we figure there are another nine million we haven't." They came from America to look for birds, to sample Priorat wines and to catch flies. They walked and talked and told us all that had caught their patient eyes. A pine martin visited them in the garden and Joe stood for hours listening to Sardinian and Cetti's warblers in the hope of a glimpse of a hoopoe.

And we talked of their eagerness for change in America, of their belief in their senator, one Barack Obama.

This drew from us tentative questions of what it must have been like for a liberal young white person growing up on a farm in Alabama. Joe's experiences and all their opinions were as compelling and uplifting as their contagious enthusiasm for nature.

Mike, who travels the world bug hunting for science, was bubbling with energy, and declared on his arrival that he hoped to sample the finest wines and to catch one specific species of fly (More mind-boggling info – there are more than 120,000 identified species of them).

So he set elaborate traps on the farm, along the valley and even among dunes on the coast – great nets that looked like small tents. He smilingly and patiently explained to Joe-Joe what he was doing and why, and lent him his net.

On the last evening, while Mike bagged up for shipping back to the States thousands of flies including, thankfully, at least one of those he was seeking, Joe showed Joe-Joe the little x10 magnifying glass that lives in his pocket.

"You've just got to have one of these, because there is something amazing, truly staggering, which is right under our noses and we don't see it."

Before returning to Illinois, both couples made priceless gifts of wisdom and wonder to our son and to us all. Now we will see where it will lead; hopefully to a fantastic journey, brief or long who can tell, yet away from the television, the computer and a world that increasingly doesn't notice the detail. Tall Ella is 13 now, her first year at high school has ended for the long summer, and I have had to nail an extension to the top of the kitchen bookshelf where our children's birthday heights are logged.

She has also just finished filming Jugamón – World at Play – for the Catalan television channel TV3, which took us high inland for the last programme.

We headed from the dramatic valleys of the Priorat to the high plain of Lleida, to the small city of the same name hugging the flooded river Segre.

It was early on a Sunday. The highway was quiet and we slowed to watch the mighty river Ebre raging through the town of Flix. The month of May was one of the wettest on record and all talk of drought has been washed away for this year at least. Thunder rolled across the high plain where we could see forever, and we were thumped by the sense of space and the truth that Spain has several million fewer inhabitants than Britain yet is nearly two and a half times the size.

We left Ella with the film crew for her day of interacting through play. Jugamón is a simple idea, but a precious one. The children see how each other live, learn a little about their new friends' backgrounds. They speak Catalan and play in Catalan, but these are children from around the world.

Then we had a blunt lesson in why such programmes are vital. The flea market on the Rambla was in full swing. Maggie, Joe-Joe and I weaved slowly through the crowd. Locals were selling books, brass ornaments and other bric-a-brac; immigrants were trading second-hand clothes and shoes out of carrier bags.

There, and in the other quieter streets, the great number of non-Catalans was manifest. Lleida's immigrant population has rocketed in the last seven years, drawn by the seasonal labour in the area's sprawling fruit orchards. It is a shock, a radical shift which, in this one place, brings into sharp focus the tides of people rolling into Catalonia, Spain, Europe, the whole world. And with such sudden differences there comes, of course, since time immemorial, fear and friction.

The ancient well of wisdom tells us, of course, if we choose to heed the reason we are all blessed with, that we must always strive to talk, to communicate, to integrate, to tolerate, to understand one another – however hard that might seem. And, just for the record, when all the parents sat down for lunch as has been the custom, we talked and laughed with a Muslim mother, whose fluency in Catalan and Spanish was humbling.

These so-called lunches (we never ate before 4pm because filming consistently took longer than predicted) always featured local fare. The paella we enjoyed beside the rice fields of the Ebre Delta was particularly enjoyable, although we nearly missed it on account of a car ahead of us veering off the high, wiggly and very wet lane into a flooded ditch. Scary. The overloaded Renault 6 landed the right way up – phew – but the woman passenger needed an ambulance.

At Lleida we had ample time to ponder what was for late lunch. We had gone from the flea market to a country park and whiled away some time watching a bold hoopoe feeding a chick in a willow tree hollow just a few metres from a crowd of children.

Meanwhile, for lunch I imagined a fruit dish of some kind and my tummy duly prepared itself for something refreshing and cleansing. And the local delicacy? Snails. A veritable lorry-load.

A word about water: we could not survive without the swimming pool, because it is a vital ingredient for holiday house guests in the high summer. Back in April we wondered if the drought might spell its end. It is a labour, and though much appreciated, it is not, between you and me, by any means the best swimming to be had here in the mountains.

Under the general themes of close to nature and isn't it great to be eight, we had a picnic by the high river, where at certain times fresh water cascades from pool to pool. There Joe Joe and Ella and aunty Liz swam to all our hearts' content.

Flying visitors to Mother's garden

Okay you birders – here is Joe Maddox's Mother's Garden list.
Common Wood Pigeon, Eurasian Collared Dove, European Bee-eater, Eurasian Hoopoe, Common Buzzard, Bonelli's Eagle, Long-tailed Bushtit, Eurasian Skylark, Common Swift, Eurasian Treecreeper, Eurasian Magpie, Eurasian Jay, Carrion Crow, European Serin, European Goldfinch, Common Chaffinch, European Greenfinch, Barn Swallow, Common House Martin, Great Grey Shrike, White Wagtail, European Robin, Rufous-breasted Bush Robin, Eurasian Golden Oriole, Great Tit, European Crested Tit, Coal Tit, House Sparrow, European Green Woodpecker, Firecrest, Common Starling, Cetti's Warbler, Orphean Warbler, Eurasian Blackcap, Melodious Warbler, Eurasian Reed Warbler, Common Chiffchaff, Winter Wren, Common Blackbird.

Martin Kirby's Norfolk novel, Count The Petals Of The Moon Daisy, is published by Pegasus (ISBN 9781903490297). See www.mothersgarden.org.