There are over 890 species of ants in Costa Rica, below are some of the varieties that cause issues for humans.
Cutter Ants (Zompopos) - You will see these industrious insects marching in long lines, holding leaf and flower cuttings over their heads.  Each ant can carry pieces of foliage weighing up to 50 times their own body weight. ​Their path creates a visible and worn trail to and from their nest.  Nests grow to sizes of 30 meters across.  Their hierarchical society is second only to humans in complexity.  Living in massive colonies of up to 5 million members,  the cutters use the leaf cutting to cultivate a fungus from which they feed. Biologists estimate that cutters manage to harvest as much as 15 percent of the foliage (including your landscaping) in neotropical forests for their fungal gardens.
Carpenter Ants - Carpenter ants enter homes in search of food, and an occasional ant indoors does not necessarily signal the presence of an infestation. Colonies of golden carpenter ants are comprised of large major workers whose tasks include colony defense and food gathering, and smaller workers who also gather food but attend to the queen and brood as well. However, the presence of large numbers of wingless workers and winged reproductive queens and males inside is indicative of an infestation. The carpenter ant colony must be located and destroyed, damaged wood should be removed and replaced, and any conditions leading to the founding of the colony, such as leaking pipes or other conditions creating wet wood, must be fixed to prevent recurring infestations.
Sugar Ants - Ever leave behind the tiniest sweet crumb or drip of syrup on a countertop or floor, only to come back a short while later and find a group of tiny ants feasting on it?  If you have these pests nesting in your home, it’s really no surprise. That’s because ants have exceptional odor-sensing abilities—and sugar, in just about any form, is highly attractive to many ant species.  Ants are often sweet-seekers, grease-eaters, or everything-eaters.  Don't let dirty glassware, utensils or plates sit for long, inside or outdoors, and keep all floors, sinks and counters clean.
Army Ants (Chutiya) - also known as "cleaner ants" because they will invade homes and cart off any live or dead insects, eggs and tiny animals they find... including scorpions, spiders, wasps and bees.  Thousands of them will swarm inside and outside for up to several hours, trails of them running on the floors, up the walls and into the ceiling, but they usually leave before nightfall.  Trails that are formed can be over 20 m wide and over 100 m long.  Nomadic army ants do not have a permanent nest but instead form a temporary nest with their own bodies.  These bivouacs tend to be found in tree trunks or in burrows. The ants hold onto each other's legs and build a well organized ball structure.  Stay out of their way, they have a nasty bite.  If they raid your home, do not try to kill them, just leave for a few hours and come back to a home free of vermin.