How do cobwebs form in a house?
Unfortunately, if you have cobwebs, you also have spiders as housemates—mainly those of the species Theridiidae (look it up and it will gross you out). They form webs in corners, crevices and even on walls in the home to catch prey or lay eggs. The webs are hard to see because they are thin strands of silk.
However, when these spiders abandoned their webs—perhaps to find a better hunting ground for prey—the webs attract dust, pollen and even have remnants of their kills stuck to them.
An entry on www.maids.com says to prevent cobwebs from forming in your house use scents that drive spiders away. As they taste with their legs, they won’t enter an area that has traces of lemon, peppermint, or eucalyptus. Dab some of these flavors onto small cotton balls and hide them inside the cracks you can’t seal, or spray the scents directly in the corners of your home.