Firstly, I don't think your humanoid creatures would have troubles with predatory arthropods larger than 1cm by the fact that they'd be just too small to be viable prey - which cuts down the size of the enemy they'd likely be facing. A five centimetre tarantula, for example, has fangs much too broad to cause any damage to a 0.2mm creature. To the tarantula these may as well be parasites.
Assuming they are warm-blooded and potentially mammalian, your creatures could live in a cold climate where arthropods would be slowed by the low temperature. They would likely build into a defensive structure such as a rock wall or earth, much like ants, where they are able to control the access points and the temperature of their dwelling.
An alternative option is to become a parasitic host to a large mammal, such as a dog or a cow, where they can live in relative warmth within the fur of the creature and even harvest its blood/flesh for food. By tying the hair into barriers and shaving large clearings of hair around their safe area, they can create barriers to other parasites.
Another alternative would be to dig a burrow into a narrow tree where they can set up splinter barriers against things climbing up - or down - the bough of the tree.
Keep in mind that the biggest enemy to your creatures is not predators, but the environment. Sudden changes in temperature, flooding (a small population can drown in a single drop of water) or fire would be enough to kill a population that would fill a small country.
Finally, addressing the most core of your question - if they have access to spider silk it is most likely that they would set up a series of complicated webs to trap and hinder any arthropods that would trespass on their territory - though setting up such an area would be a massive undertaking for a people so small.