Sally Scalera

Brevard County Horticulture Extension Agent
3695 Lake Drive -- Cocoa FL 32926 -- 321-633-1702

Brown widow spider sacs help identify

May 4, 2002

(Pictures courtesy of Fred Santana, Ph.D., Sarasota County IPM Coordinator)

We have a large population of venomous brown widow spiders in Brevard County, and they are just as dangerous as black widows.

Brown widows are easy to identify by their egg cases and markings, but they can range in color from cream to black.

brown widowMost people are familiar with black widows, which are shiny, jet black, and normally found in shady, damp places such as piles of chopped wood. Brown widows are different in that they can spin a web in the middle of your lawn in full sun. They can be found in the landscape, under patio furniture, on the handle of your trashcan and even on playground equipment.

brown widow egg sacThe brown widow has a red or orange hourglass mark on its abdomen. Brown widow spiders produce an egg sac that resembles a World War II water mine, which is white, round and has spikes all over it.

Because the brown widow can vary in color, many people don't immediately recognize it as a venomous spider. They also have spots on their backs (or stripes if they are young). Dark bands are on their eight legs where the segments attach.

markingsBrown widows are so poisonous that they could possibly kill a small child or pet. An adult with health problems also could be at risk.

Like most spiders, widows are shy and will not bite unless aggravated. The bite of a widow spider is not always felt, but usually feels like a pinprick. The initial pain disappears rapidly, leaving swelling where tow tiny red spots appear.

Muscular cramps in the shoulder, thigh, and back usually begin within 15 minutes to three hours. If you suspect a widow spider has bitten you, try to capture the specimen for identification and immediately consult a physician.

All of the widow spiders reproduce rapidly. One female can produce up to 18 egg sacs. Each egg sac can contain about 250 eggs. Once a widow is found, it indicates a widespread infestation which can be difficult to eradicate.

Non-chemical control of spiders is usually effective in reducing their populations. Outside lights should not be left on at night. Large number of fling insects attracted to lights cause spiders to be numerous around garages and under eaves.

Trash, lumber piles, bricks, weeds, and outside structures are good breeding places for spiders and should be cleaned up. Inside the home, spider webs should be brushed down. The egg sacs should be destroyed to prevent hundreds of young spiders from emerging.

Vacuum cleaner attachments may be used to clean walls. Dispose of the collected debris.

Inside buildings, space sprays containing pyrethrins or pyrethroids are effective in killing spiders. Space sprays have little residual activity and should be applied when spiders are noticed. One such product listed for use is CB-38 Extra.

For some residual control, there is Conquer (emulsifiable concentrate). It should be applied as a coarse wet spray to surfaces where the spiders are found. Pay particular attention to cracks, crevices, and similar protected locations in floors and walls. Spray directly on insects when possible. Another product for the same sites is Cynoff EC Insecticide (emulsifiable concentrate).M/p>

So take some time to check around your yard, patio, porch, and garage. Be on the look out for a three-dimensional, loosely scattered web that may have the recognizable egg sacs.