San Antonio’s warm, humid climate makes it one of the most pest-active cities in Texas. From fire ants colonizing every yard to mosquitoes breeding well into fall, the city supports a wide range of insects year-round. Whether you just moved to the area, are dealing with something crawling across your floor, or want to know what to watch for outdoors, here’s what lives alongside you in San Antonio and what actually matters for your health and home.
Mosquitoes: Active March Through November
Mosquitoes are San Antonio’s most persistent warm-weather pest. Breeding kicks off with the first warm, wet weeks in March and builds through spring. Peak activity runs from June through August, when long evenings and higher humidity give mosquitoes more feeding time, especially around patios, pools, and outdoor seating areas. What surprises many residents is how late into the year they stick around. Warm fall days after late storms keep mosquitoes active well into November, and in milder winters, eggs and larvae can survive in hidden pockets of standing water.
The real concern is West Nile virus, the leading mosquito-borne disease in the United States. About 80% of people infected never develop symptoms. The other 20% typically get a mild illness with fever, headache, body aches, and sometimes a rash. Roughly 1 in 150 infections leads to a severe form that can affect the brain and spinal cord. Symptoms appear 2 to 14 days after a bite. In warmer parts of Texas, there’s year-round risk whenever mosquitoes are active. Eliminating standing water in your yard, even small amounts in plant saucers, gutters, or old tires, is the single most effective thing you can do.
Fire Ants Own Every Yard
Red imported fire ants are everywhere in San Antonio. If you have a lawn, you have fire ant mounds, or you will soon. Their stings produce burning, itchy welts that can last for days, and some people have severe allergic reactions. Children and pets are especially vulnerable because they may stumble into a mound before realizing what’s happening.
For yards with heavy infestations (five or more mounds per quarter acre), the recommended approach is a two-step method: broadcast a bait product across the entire yard, then treat individual nuisance mounds directly. If you only have a few mounds, treating them individually helps preserve native ant species that actually compete with fire ants. Mounds near your home’s foundation deserve priority since foraging ants can find their way indoors through small cracks. For vegetable gardens, most chemical baits aren’t labeled for use inside the garden itself, but applying bait around the perimeter works because foraging ants carry it back to their colonies. Very hot water poured directly into a mound is a chemical-free option, though it takes care to avoid scalding nearby plants.
Termites: Billions in Damage, Often Invisible
Termites are the most destructive wood-damaging insects in the country, responsible for billions of dollars in damage each year. The most common type found in San Antonio homes is the native subterranean termite, but Formosan termites have also been discovered in Bexar County, and researchers at Texas A&M are concerned about their spread. Formosan termites are extremely aggressive wood eaters. Unlike native subterranean termites, if a Formosan colony gets separated from its queen, it can survive and keep eating. They also spread rapidly by establishing new nests.
Swarming season runs from April through June. This is when most homeowners first notice a problem. Swarmers are winged termites that leave the colony to start new ones, and they’re drawn to lights. Look for winged insects near windows and doors, small piles of discarded wings on windowsills, mud tubes running up your foundation, or baseboards that feel soft or blister when you press on them. During the hotter months from July through September, termites move deeper into soil and wood, making damage harder to spot even though they never stop working. Regular inspections, particularly in spring, are the best defense. Liquid soil treatments around the foundation provide a chemical barrier that can significantly reduce the risk of infestation.
Kissing Bugs and Chagas Disease
This is the bug most people don’t expect. Three species of kissing bugs live in Texas, and South Texas falls squarely in their range. Adults are half an inch to an inch long, dark brown or black, often with orange or red striping along the edges of their bodies. They feed on blood at night, typically biting around the face and mouth while people sleep. The bites themselves are painless, so most people never feel them.
The real danger is what comes after the bite. About half of kissing bugs in Texas carry a parasite that causes Chagas disease. The parasite doesn’t enter through the bite itself but through the bug’s feces, which it deposits near the wound. If you scratch the bite and rub the feces into the wound, your eyes, or your mouth, infection can occur. The acute phase lasts a few weeks to months and may cause fever, fatigue, body aches, headache, or diarrhea, though some people have no symptoms at all. About 1 in 3 infected people eventually develop chronic Chagas disease, which can cause serious heart problems.
Dogs are also at risk. Chagas infection in dogs can cause heart disease, digestive problems, and in some cases sudden death, though many infected dogs show no outward signs of illness. Keeping outdoor lights off near doors at night (kissing bugs are attracted to light), sealing cracks around windows and door frames, and checking pet sleeping areas can reduce your exposure.
Scorpions: Painful but Not Dangerous
The striped bark scorpion is the most common and widespread scorpion in Texas, and San Antonio residents encounter them regularly, especially in garages, closets, shoes, and bathtubs. Stings are painful and produce local swelling, numbness, and itching that can persist for several days. Reactions vary based on individual sensitivity, ranging from mild discomfort to strong swelling and discoloration. The good news: no scorpion species in Texas is considered lethal to humans. Deaths attributed to the striped bark scorpion are not well substantiated.
Scorpions enter homes looking for moisture and shelter. Reducing clutter, especially in storage areas, and shaking out shoes and clothing left on the floor are simple habits that prevent most surprise encounters.
Spiders, Flies, and Other Indoor Pests
San Antonio’s climate also supports healthy populations of house spiders, brown recluses, and black widows, along with seasonal waves of flies and roaches. Keeping yards tidy and removing debris reduces spider habitat near your home. Regularly clearing webs from corners discourages spiders from settling in. Flies become a bigger problem in summer. Fly traps placed both indoors and outdoors help, but the foundation of fly control is keeping food covered, cleaning up spills quickly, and taking out trash before it accumulates.
Seasonal Prevention That Actually Works
San Antonio’s pest pressure follows a predictable rhythm. Spring, as temperatures climb, is the time to inspect your home’s exterior for cracks or gaps and seal them with caulk or weather stripping. Pay attention to where pipes and wires enter the house, gaps under doors, and spaces around window frames. This is also when termite inspections matter most.
In summer, shift your focus outdoors. Walk your yard weekly to dump standing water, check for new fire ant mounds, and monitor for termite signs along your foundation. Fall brings a different challenge: rodents, roaches, and other pests start seeking shelter indoors as nights cool. Clear away fallen leaves and yard debris that give pests cover near your home. In winter, store food in airtight containers and maintain the seals you applied in spring. San Antonio winters are mild enough that many pests stay active at reduced levels rather than fully shutting down.
The consistent theme across every season is exclusion. Sealing entry points, eliminating food and water sources, and reducing harborage near your home’s exterior handles the majority of indoor pest problems before they start.