Actually, unlike other insects, spiders in general do not groom themselves, it's not just the brown recluse. Powders can kill insects and spiders other ways than ingestion. Powders can also cut the outer layer on insects and spiders which makes them dehydrate because their waxy protective outer layer does not hold in moisture anymore. Also, when treating for spiders usually the spray and dust is applied more to get rid of the other insects around which is the spiders food source. If there are no other insects around for the spiders to eat, the spiders will not want to be around anymore. In addition to dust, we do have a
Spider Control Kit which has a spray for the exterior of your home and glueboards for inside to monitor your insect situation. Glueboards are great for catching spiders.