Black widow or brown recluse: how to tell them apart

The female black widow (Latrodectus mactans) is the spider most people picture: glossy black, with a round, almost bead-like abdomen and a red hourglass on the underside. Her body is about half an inch long and her legs are long and thin. Males are much smaller, often brownish with pale markings, and they rarely bite. Young widows can be patterned in orange, white and tan before they darken, which catches a lot of people off guard.

The brown recluse (Loxosceles reclusa) is plain by comparison. It is tan to medium brown, roughly the size of a quarter with its legs spread, and it carries a darker violin-shaped mark on the front body section, with the neck of the violin pointing back toward the abdomen. The legs are one solid color, with no bands or obvious spines, and the abdomen has no pattern at all.

Plenty of harmless brown spiders get blamed for being recluses, so look for the violin and the plain legs together. A simple rule covers most cases: shiny black with red usually means widow, and dull brown with a violin and nothing else may mean recluse. If you are unsure, trap the spider under a jar and have it identified before assuming anything.

The two species split a property roughly between outdoors and indoors. Texas A&M AgriLife lists woodpiles, water meter boxes, the underside of eaves, garages and boxes as typical black widow spots. Recluses prefer the indoor side, from closets, boxes and stored clothes to the garage and the gap behind baseboards, and they are seen most from April to July, their mating season, when males roam. The garage is where the two ranges overlap, which is why we look it over carefully on any spider call.

In and around Amarillo houses, these are the places each one turns up most:

• Black widow: under the lids of water meter and sprinkler valve boxes.
• Black widow: in stacked firewood, lumber, landscape timbers and block walls.
• Black widow: beneath patio furniture, grills, flowerpots and outdoor toys.
• Brown recluse: on closet floors, inside boxes and in clothes left untouched for a season.
• Brown recluse: behind baseboards and furniture pushed against outside walls.
• Both: along garage walls, in boxes sitting on the slab and inside gloves or boots left on the floor.

Prevention for both spiders comes down to fewer hiding places, fewer insects to eat and fewer gaps to walk through. Spiders follow their food, so the crickets, roaches and moths that collect around porch lights and garage doors on summer nights draw spiders in behind them. Yellow bug lights, and fewer fixtures left burning all night, shrink that supply.

A few habits make the biggest difference:

• Wear gloves when you move firewood, carry out stored boxes or clear the garage.
• Flip a water meter or valve box lid with a tool, not your fingers.
• Pack garage and closet storage in plastic tubs with snug lids, up off the floor.
• Shake out shoes, gloves and jackets that have hung or sat unused for weeks.
• Knock down tangled webs in garage corners and under the eaves with a long-handled broom.
• Replace worn door sweeps and fit mesh into the weep holes along the brick.
• Keep the woodpile raised on a rack and several feet from the siding or brick.