The spiders are generally found in tropical areas but were reported along the Mississippi Gulf Coast last year.
Entomologists with the Louisiana State University AgCenter say the spiders likely migrated from Florida through commercial imports of plants, food, building materials, or furniture.
LSU entomologist Dennis Ring is advising Louisiana residents to wear gloves, long-sleeved shirts and long pants when working outdoors, especially in areas that don't get a lot of human activity.
Though less aggressive than the black widow, "its venom is more toxic than the black widow's," Ring said. "But it doesn't put out as much venom in its bite."
Ring says the brown widow can grow to 1 1/2 inches long. It is brown or grayish-brown instead of black and has a yellow-to-orange hourglass design on its underside, as opposed to the familiar red hourglass design on the black widow.
It also has black and white marks on the top of the abdomen and often has dark bands on its legs, he said.
Ring says the spiders are most often found in areas that haven't been disturbed, such as brush piles, wood piles and areas where hurricane debris has accumulated. They also can show up in crawl spaces, under chairs, in garbage can handles and under flower pots, eaves and porch railings, he said.
The Florida Department of Agriculture lists the most common symptoms of a widow spider bite as intense pain, rigid abdominal muscles, muscle cramping, malaise, sweating, nausea and high blood pressure. If untreated, symptoms usually last 3-5 days.