While a men's shelter in Mesa is confronting a problem with bed bugs, students and teachers at a Gilbert elementary school last month found tiny bites on their arms and legs from an irritating insect: the flea.

Students at Spectrum Elementary School brought home a letter on April 22 from the principal about the flea problem, which state health officials confirmed. The case prompted a thorough cleaning of the school and a visit from the exterminator.

No children became sick. Gilbert Public Schools spokeswoman Dianne Bowers said three staff members and one child complained to the Spectrum Elementary nurse of "bugs that bite."

A mother of three at Spectrum, Christine Accurso, said she and a few other parents recall seeing bites on their children.

The school's flea problem surfaced several days after word of a bed-bug infestation at the East Valley Men's Shelter in Mesa. A New Leaf, a non-profit operator of the shelter, says that it has been trying to eradicate the pests and that a long-term extermination plan could cost close to $100,000.

State health officials and a longtime University of Arizona entomologist and curator said the bed-bug problem is becoming more common nationwide as more people travel frequently and carry tiny stowaways on blankets, pillows, clothes and suitcases.

But the experts said the Gilbert school's recent flea encounter, which they emphasize was harmless, was a rare situation. Rarer still was the culprit.

State health officials believe the flea responsible was the Pulex irritans - a human flea. It is slightly larger than the head of a pin, with a body that spans at least 2 millimeters.

Without additional samples of the insects, it's hard for scientists to positively confirm the creature's identity.

Carl Olson, the UA entomologist, noted the school sent a female flea sample to the Arizona Department of Health Services.

Like female birds, many female insects are much duller in color and detail than their male counterparts, he said. This makes them harder to identify.

The flea "is a real complex species group," Olson said.

"We're pretty good as entomologists, but there's too much for us to know," he said of the vast flea species and constantly expanding field of entomology.

Count the fleas and bed bugs among the dozens of insects that depend on our flesh and blood for survival.

Olson said mosquitoes are more likely than fleas to hang around a school because irrigation systems and poorly maintained backyard pools provide the ideal wet habitat for breeding.

Fleas, meanwhile, are more often found on animals or household pets such as cats or dogs.

Gilbert officials had the entire Spectrum Elementary School cleaned after confirming a student had flea bites. Although only a handful of people had bites, an exterminator was sent to spray pesticide campuswide two weeks ago. The exterminator visited again last Saturday.

Olson said spraying is often the first response, but can be more harmful than helpful. Chemical particles in the pesticide are toxic and can "grasshopper" to various parts of the room, floating and attaching to items or locations other than where they were targeted.

Many, such as nocturnal bed bugs, can be deterred with simple tactics such as leaving the lights on.