As any parent knows, there's more to summer with small children than keeping them cool. There's the matter of curiosity, as insatiable sometimes as their quest for the latest beverage. Here are some ideas to help quench -- for both you and your child -- the August thirst for new experiences.

Walking straight up the middle of a shallow stream in new blue boots looking for fossil mud worms could be better than King's Dominion to a 4-year-old.

Water, sand, rocks, and a new idea to think about -- there are live worms under most rocks and there are worms that built their homes in mud flats millions of years ago -- are enough to keep a lot of people happy for hours.

There is also the special pleasure of an interest shared between parent and child, whether it's fossils, rocks, worms, or the delight in finding that neither of you minds getting wet if you're having a good time. (You'll drip-dry nicely in the sun.) But if getting wet bothers you, bring a towel and extra pants.

Long Branch Nature Center in Arlington is the best place I know to go stream-walking. The nature center itself features an enormous snapping turtle, a table full of animal and snake skins, antlers and bones that children can handle, plus the necessary bathrooms. But it's the stream below that is a delight to explore.

The fossil worms appear as lumpy lines in orange-brown sandstone. Cobbles continually break off and wash down into area streams from the mountains. Mica schist, quartz in diffeent colors, and most of the other rocks common to this area can be found here. Just around the stream bend are two long bridges that are fun to crawl across. Cray fish build their mud castles along the banks.

It's probably a good idea to remind children that stream-walking is something you come prepared for (boots, extra clothes). You need a shallow stream and an adult.

The Arboretum duck pond is a great place to feed the fish. For young children who like the idea of fishing, but can't face putting a worm on a hook, tie a string to a dowel from the hardware store; tie the other end of the string to a hard piece of bread, and have him hold it out in the water.

The pond is deep, so you'll want to stay right beside him. In a few minutes, he'll have a school of small fish nibbling the bread and pulling his line. The thinner the dowel, the more fun. He's never going to catch anything, but if he's really interested in fishing, you can tell him he's practicing. (In a couple of years he can take a rod over to the Little River side of Roosevelt Island and catch sunfish and spots.)

Most children are really interested in bugs. I never was until my 5-year-old suggeted I might like to pet a caterpillar he had spent the morning with. That was a new idea, but it made sense. After all, it had fur and things with fur are nice to pet.

If your child is interested in bug-hunting, you can make a trip to the Smithsonian's Insect Zoo first to get the names of things and where to look for them. But it's just as easy to get a copy of the Golden series, "Insects," ($1.95), an aquarium fish net, and an old margarine tub with a top, and go out to Kennilworth Aquatic Gardens.

Water striders and water boatmen skid around on top of most ponds and are easy to catch with a plastic tub. Turn them over and see if you can count the six legs that make an insect an insect and not a spider. Look at the eyes and mouth parts with a magnifying glass. Put them back in the water and watch the way they move.

Some water bugs camouflage themselves through movement. The backswimmer, for instance, swims upside down and backwards so that any predator looking up from the bottom of the pond, sees only his blue back which blends with the sky.

Some bugs look very different at different stages of their life cycle. A black beetle-like bug that lives in the water and bites everything grows into a dragonfly the size of a small bird with a pale blue and black body and black-lace wings.

Orange and black milkweed bugs, bright green stink bugs, walking sticks, inch worms, daddy-longlegs live on the foliage at the edge of the ponds. If you bring along a set of magic markers, you can draw what you find before you let it go.

The best reason for not taking anything live is not necessarily the Park Service sign, but the fact that if you don't know what it eats, it's going to starve to death. Most children who have ever forgotten their lunch box can sympathize with that.

While you're fishing around for water bugs, you will probably catch the tiny transparent fish that feed on mosquito larvae. The ponds are full of tadpoles in all sizes, from half an inch to nearly half a foot. The big ones take several years to grow into frogs. You have to be quick to see full-grown frogs before they plop into the water. Turtles sun themselves on lily pads.

You may see Chinese lotus plants standing 5 feet high in the water with pink petals and yellow-bell centers. Children enjoy seeing drops of water rll around like marbles on lily pads, a great example of waterproofing.

There is also natural clay here. With enough siftings, and washings, you can get it clean enough to fire a kiln. But most children just like to muck around with it, making pinch pots or crazy animals, then wadding it up and making something else. The fact that you "found" it makes it special.

The Aquatic Gardens, like any city park, is a good place not to take a purse. Wear old clothes, stick $2 in your pocket, and carry lunch in a bag over your shoulder.