Though they are related to spiders, daddy long legs are not actually spiders but arachnids in the order Opiliones. They typically spend most of their time outdoors but sometimes find their way into cellars and homes. Though urban legends claim that their venom is deadly, daddy long legs are not venomous and pose no danger to humans. In fact, they eat other insects, offering a benefit to humans, so you may want to think twice about getting rid of them unless your house is overrun with the leggy critters.
Stroll Through the Great Outdoors
To get into your home, daddy long legs must first visit your yard. Do some clean up outside by moving wood piles well away from the house and cutting bushes back so that they aren't directly up against the walls. Remove hiding places like unused lawn furniture to make your yard less attractive. Swap the bulbs in your outdoor light fixtures for yellow ones, as these are less attractive to daddy long legs and insects.
Secure the Perimeter
Daddy long legs enter homes through torn screens, cracks in walls and gaps around windows. Keep them out by replacing torn window screens and caulking cracks and gaps. Check exterior doors for gaps and replace the weatherstripping if necessary to seal the space under and around the door. This will help keep both daddy long legs and their food supply from entering your home.
Daddy long legs absolutely love clutter. Stacks of boxes and piles of old magazines are some of their favorite places, so remove this type of clutter from your home. After a good de-cluttering, vacuum thoroughly around your baseboards, behind furniture and underneath furniture. If you see any daddy long legs, egg sacs or old spider webs, suck them up in your vacuum cleaner too. Be meticulous, vacuuming up under tabletops and around beams in your basement. The more careful you are the more unwanted guests and hiding places you can remove, so clean like your mother-in-law is coming to visit and bringing her white inspection gloves. When you are done, seal the vacuum cleaner bag and throw it away in your outdoor trash can right away.
Treat the Home
Treat the baseboards of your home with a pesticide to kill any daddy long legs that find their way into your newly cleaned building. Boric acid is one low-toxicity option. Boric acid works by contaminating the body of pests as they walk through it. The chemical is later ingested when the insect grooms itself. To apply boric acid, dust a light coating around baseboards and in cracks and crevices. You should barely be able to see the powder when you are done. Do not use boric acid where pets or children can come in contact with it, and never apply it near food-preparation areas.