Oh, how well we pet owners know the sound, especially at lights out for bedtime. We just settle in, get comfortable, close our eyes – and it starts: that rat-tat-tat of the bell or the tag on the collar as the back leg starts working furiously, endlessly, on an itch. Or worse, with dogs, mostly: They get those tiny front teeth working on a tickly spot that just sounds wetter and snortier as they go. And we lie there in the dark, waiting for it to end and hoping they don’t just start up in a new place just as soon as they finish the first one, but they do.

It’s flea season again, and these nasty little buggers don’t care a mite about the threat of global warming. In fact, the earlier in the season that temperatures hit 65 degrees and humidity at 67 percent to 75 percent, the happier and more (re)productive they are. They spell torture for dogs and cats, and once they get in your house and multiply, they’re equally happy to burrow into your sock bands and chew away on your ankles, too.

If you think you have a visual bead on a flea, it will use these incredible legs to pull a disappearing act as it searches for a dark hiding place; and if you manage to capture one between your fingers, don’t think simply squeezing will kill it. Their bodies are hard and durable, and likely when you open your fingers, it will jump away again.

Scratching is your first best clue as to whether your pets have fleas, but if you’re still not sure (some animals simply have grass allergies), separate the fur on the animal’s inner thigh or belly, or the spot right above the tail, and look either for movement of the fleas themselves or for flea dirt – the peppery-looking stuff that is most easily seen on light-colored surfaces. This dirt is actually the fecal matter left behind by fleas, who feast on their warm-blooded hosts two or three times a day. If you put this dirt on a damp surface, it will leave a stain that looks like blood, because that is mostly what it is.

If your animal is leaving behind a salt-and-pepper-looking mixture, you’ll know you’re at an advanced stage of the flea life cycle: The white things are flea eggs, being laid at a rate of between 20 and 30 a day by each female. That’s hundreds of eggs per female, each of which will hatch into a new breeding machine in short order under favorable conditions of warmth, humidity and availability of four-footed feeding stations.

Flea eggs develop wherever they land, and they hatch into larvae that feed on all manner of unpleasant things, including flea dirt, in your carpets or furniture. These larvae grow and develop, pass through two moltings, and then form into pupae, protected by a cocoon that allows them to survive longs periods of time and extreme conditions (even freezing) until temperatures are right to hatch as adults and start the cycle again.

It’s important to catch the signs of fleas early and to eliminate the problems, or better still to avoid them altogether. The itching itself, or “pruritus,” is uncomfortable, but in addition, many animals have allergies to flea saliva, and even a bite or two can produce a reaction much like what we experience from mosquito bites. The scratching and biting then leads to large patches of hair loss and open skin wounds that in turn can become infected. Also, massive flea infestations on animals actually can cause anemia, because each flea on your pet is enjoying several free meals a day for several weeks, and that can amount to a significant blood loss over time.

The final insult is that fleas are a crucial step in the life cycle of the tapeworm (the ones that leave little segments that look like rice), so it’s almost a certainty that if your pet has one of these pests, it will have the other as well. And remember that tapeworms can be passed on to humans, especially to children.

What we want to do is break the flea’s life cycle and clean up the living environment. Don’t even waste your money on flea collars. Topical systemics are much safer and more effective, and many good products are out on the market that will poison the flea when it bites your pet. But please be cautious about products you can buy at discount stores: One well-known brand went through a long spell of legal problems because its product was causing sickness and sometimes death in the pets. It’s best to visit with your vet to find out which products he or she recommends.

Also, as you tackle the flea problem, remember to vacuum the carpets and furniture well (and throw the bag away – the eggs and larvae can live and hatch in there as well), and always wash all bedding in hot, soapy water. If you don’t clean up the source, the fleas may reappear. Inside foggers and sprays are also useful weapons in the battle.

Staying alert for signs of problems, and using preventative measures should provide an effective front in the flea battle. Your pets will be glad you did.