Why the Brown Recluse Spider is difficult to eradicate

There are several reasons why the brown recluse spider is so difficult to eradicate:

1.    Unlike insects, spiders do not clean themselves. Thus they do not typically ingest residual traces of insecticide just by crawling across the floor.
2.    Brown recluses, unlike other spiders, don’t ingest insecticide that might be sprayed on a prey-catching web. This is because they do not spin webs to catch prey and rarely use their silk.
3.    Female brown recluses often live inside walls, boxes, or other out of the way places where pest control companies do not spray.

4.    Male brown recluses typically hide out during the day when pest control companies do their spraying.
5.    Unlike most spiders, brown recluses prefer dead prey over living prey. For this reason, when pesticides kill insects it only makes their lives even easier because they don’t have to kill anything to have a meal. Less energy is spent and they can go longer in between meals as well.

In fact, brown recluse spiders can eat an insect killed by insecticide just 24 hours prior. They will even feed on insects that have been dead for up to two months!
6.    Research conducted at Oklahoma State and Texas A&M Universities confirm that brown recluse spiders are tenacious and are not killed by most insecticides, unless sprayed directly on the spider. However, even a spray of water can kill a brown recluse.
7.    When pesticides are used, the more mobile male brown recluses simply flee the house en masse, as has been proven by researchers at Kansas University who set pitfall traps outside entry/exit points of homes that were being treated. Probably others were going to their favorite hiding place if they weren’t hiding there already.

8.    House spiders that are tremendously beneficial in the battle against brown recluse spiders can be killed by the pesticide, eliminating both competition for insects and potential enemies.

So the bottom line is you cannot necessarily completely eradicate the spider with 100 percent certainty. The only thing you can do is hope to contain them… especially in areas where they are indigenous.

Brown recluses live both inside and outside of the home. If you were to eliminate them all in one day, there could be more who are outside who find their way in.
Nevertheless, Kansas University researchers do make the statement that “effective population management is possible” with glue traps.

Pesticides are often ineffective with Brown Recluse spiders, and for this reason reputable pest control companies do not guarantee eradication of the spiders. Kansas University researchers state that spider traps, if used correctly, are effective for controlling Brown Recluse populations. We offer the brand used and recommended by them. See http://www.brown-recluse.com/spidertraps.html for more details.

Thomas J. Martincic
Brown Recluse Response Team