Guests that visit and never leave are not the sort you want to invite into your home. Pot plants that have been brought indoors at the onset of cooler weather often bring with them uninvited guests in the form of bugs and insects. Two of the most common are spider mites and scale insects which need to be eradicated before they damage the plant. I came across an article by Richard Hentschel from the University of Illinois which explains what you need to look out for and how to deal with the problem.

Everyone has guests over at the house once in a while and some stay a few days. We do all we can to bring our houseplants indoors for the winter without the ?insect relations? that so often accompany the plants and never leave, said Richard Hentschel, U of I Extension horticulture educator.
?Sometimes even after our best attempts you wake up some morning a few weeks after your houseplants have been inside and see something that is not quite right on the plants or maybe in the window trying to get out,? said Hentschel. ?The insects we find are not always closely associated with our houseplants, but rather happened to be on the plants at the time they were brought in.
?If this is the case, the potential for a problem is really low. These insects do not feed on our plants and without food, and in the wrong environment; we will find them dead on the window sill if we have not already disposed of them with paper toweling or the vacuum cleaner hose and nozzle.?
Box elder bugs are a great example, they will wander around the home, living on the food they have stored and you will find them later not having survived being indoors. Box elder bugs also leave behind little black spots of the food they digested, so keeping up with them is preferred rather than having to do a cleanup later.
?The insects that are troublesome outside are the ones that will cause the problems on the inside as well,? he said. ?Outdoors there are natural predators that will keep the populations in check and weather events like rainstorms that also help reduce the number of insects on the houseplants.

Read the rest at University of Illinois
Image source: Paramecium