FORT WORTH, Texas - They are up there, having a good time at your expense. Throwing wild parties and listening to rock 'n' roll.

Go ahead and laugh, but do you have any idea if there are squirrels and mice in your attic and what they might be doing? You never gave the critters a key to the house, yet they invited themselves in, and now they won't leave.

As pretty as all those trees are in your yard, providing shade from the summer heat, they are also the perfect launch pads to your roof for those little creatures that want nothing more than to turn your attic into a time share.

The dead of summer may be the only time when squirrels, mice, raccoons, rats or opossums don't want to take up residence in your attic; but once there is a hint of autumn in the air and the temperatures begin their downward spiral, that is when the vermin are like the unwanted relatives who show up at your doorstep.

"Animals can live in your house year-round, but we do see an increase right now simply because this is the time of year people are at home more and they start hearing noises," said Jason Livingston, who has worked at Critter Control for the past four years. "They can do lots of damage. But if they've been in your house for a long time, you don't notice it anymore. They just become a normal odor in your house."

A critter in your attic can be devastating to electric bills, wiring, insulation and/or air conditioning and heating ducts. If you put down poisonous bait to eliminate them, just know they may not make it out alive. If and when they are entombed in your house, the stench can last for days. So do yourself a favor and prepare now to avoid the early-morning squirrel parties and prevent the destruction a clan of critters can do to your attic.

Remember the critter-control mantra: "You've got to think like the squirrel."

Here are some steps to ensure your home doesn't become a critter's home away from home:

n Identify entry points. This is often the single hardest part of the job - how are these little home-wreckers getting into your house? To the naked eye, it may appear there are no visible holes or gaps large enough to allow a squirrel or raccoon to walk through.

"I have seen perfect new homes and there are gaps all over where animals can get in," Livingston said. "The builders themselves don't realize how to keep the animal out."

Hard-to-see entry points are often under the eaves, at corners where one piece of wood meets another, dryer-exhaust vents, chimney shafts, behind rain gutters and near ceiling vents. If there are no obvious points of entry, look for chew marks where the intruders have carved their way in.

n Set traps. You can invest in a steel-cage trap - which may run between $35 and $70 - to catch the critters yourself. The bait is often either a piece of corn or nuts, something an animal would enjoy eating. Beware, however, because setting a trap and placing a piece of food in it is neither as easy as it looks nor a guarantee of success.

"There is a methodology of trapping," Livingston said.

The trap doors are delicate, and the critter needs to walk all the way in, grab the food off the platter and have the doors lock him in. If you want to hire a company to do it, know it may charge about $50 per critter removal. There is a very good chance that if you catch one, they're going to catch an entire family, which may take several removal trips and cost several hundred dollars.

There are other, more elaborate methods - evictor strobe lights can be purchased for between $250 to $1,000.

The best way is still to use a trap, however, and there is a great deal of trial and error when you do it yourself. And rat/mice poison usually doesn't work on a critter.

n Close the doors. Once a critter's doorway to your pad has been established, it's vital to close it. It also helps not to leave any doors - even garage doors - open for extended periods. It's a virtual welcome mat for critters. Try to avoid using items that they can easily gnaw their way through, such as more wood. "Wire mesh isn't a good idea because squirrels can just pull it out," Livingston said.

Consider using materials that can't be penetrated by sharp teeth, such as steel.

Of course, if you don't think you can seal the house yourself, you can hire a company to do it, preferably those that specialize in critter removal. Catching a mouse is a much different task than killing a bug. Just be prepared to spend a lot of money. Livingston said that costs can run into the thousands.

n Act once they are inside. One option is to set up the trap in your attic. Much like setting the trap outside your home, setting the trap inside the home

isn't a guarantee for catching critters. "You never know with these guys," Livingston said. "Some animals don't like to eat inside. Sometimes, they don't want to go into the cage."

Another option is to spread fox urine - which can be purchased at hardware and home-improvement stores - throughout your attic. This method of "keep away" prompts much debate in the critter-catching community.

There are those who believe it works, and others who are sure that it's just a myth.

n Remain alert. Just because you have critter-proofed your home and you can't see or hear any evidence that you have unwelcome visitors, don't assume the battle is won. Try to "clean" out your attic so the scent is no longer there for the animals. This could mean removing all of the insulation and putting down a new base.

For all you know, the squirrels are regrouping in the backyard, deviously plotting to get back into your house.