Termite Swarm Season in Philadelphia: What to Do When You See Swarmers

Every spring, Philadelphia homeowners call us with the same alarm in their voice: "There are hundreds of winged insects near my window." If this has happened to you, this guide tells you what you're dealing with, how serious it is, and exactly what to do next.

What Is a Termite Swarm?

A termite swarm is a natural reproductive event. When a termite colony reaches maturity — typically after 3-5 years — it produces winged reproductives called "alates" or "swarmers." These swarmers emerge from the colony in large numbers on warm days following rain, mate in flight, shed their wings, and attempt to start new colonies in the soil.

Seeing a swarm is a sign that an established termite colony exists somewhere nearby — often in or under your home. Swarmers found inside a home specifically almost always mean the colony is inside your home's structure, not just in the yard.

When Do Termites Swarm in Philadelphia?

Eastern Subterranean Termites — the dominant termite species throughout the Delaware Valley — swarm on warm, humid afternoons in:

• March and April: Primary swarming period in the Philadelphia area, especially following warm rains
• May: Secondary swarming in some years
• Occasional fall swarms: Less common in the Philadelphia area but documented

Swarming typically occurs between 10 AM and 2 PM on days when the temperature is above 60°F and humidity is high. Swarmers are attracted to light and are most commonly found at windows, light fixtures, and on window sills.

What to Do When You Find a Swarm

Step 1: Don't panic — but don't ignore it

Finding a swarm is alarming but doesn't mean your home is falling down. Termites work slowly. However, the presence of swarmers means damage has already been occurring — often for years — and professional inspection is urgent.

Step 2: Collect specimens

Collect 5-10 swarmers in a sealed plastic bag or glass jar. Don't spray them. Identification is important because carpenter ant swarmers look similar to termite swarmers and require different treatment. See our guide on termites vs. ants for identification tips.

Step 3: Note where you found them

Were the swarmers at a window? Near a basement door? Emerging from the floor? Location matters enormously for identifying the colony location. Write down or photograph where you found them.

Step 4: Call for an inspection immediately

Don't wait. Call City Best Pest Control at 215-800-0029 for a same-day or next-day inspection. Termite inspections are thorough and include checking foundation walls, basement joists, window frames, door frames, and any wood-to-soil contact around the property.

What Does a Termite Inspection Find?

Our inspectors look for:

• Mud tubes: Pencil-width tunnels of dried mud on foundation walls, piers, and basement walls — termites build these to travel from soil to wood while maintaining humidity
• Damaged wood: Probing with a screwdriver reveals wood that's hollow or crumbles when pressure is applied
• Live termites: Breaking open a mud tube often reveals worker termites — pale, soft-bodied insects about 3-4mm long
• Discarded wings: Swarmers shed their wings after mating — piles of small transparent wings near entry points are definitive evidence

Treatment Options for Philadelphia Termites

Liquid termiticide: A continuous chemical barrier is created around the foundation by trenching and injecting termiticide into the soil. This is the most common and fastest-acting treatment. One application provides 5-10 years of protection.

Baiting system: Stations containing termite bait are installed around the perimeter. Termites feed on the bait and carry it back to the colony, which is eventually eliminated. Slower acting than liquid treatment but eliminates the entire colony. Requires ongoing monitoring.