Hi

Just an update: I posted the same question in advise forum and got advise that these are male ants. Ant traps will work and I will try the ant traps today.

Thanks

Kate

There just flying ants

The winged ants can be male or female, fyi.

with such large abdomens, they're likely females.

If they're about a hlf inch long, they're likely to be carpenter ants.

The once a year activity of flying ants issuing from the same site means that your structure is infested, Best thing to do is look in voids-- crawl space and attic -- for fresh sawdust. That means the colony is above the sawdust.

If all that's true, you have to repair/fix/stop the reason why you have moisture-damaged wood -- that's the favorite place for carpenter ants to nest.

You also need to locate the main nest outdoors -- it's in a dead tree/stump; or other dead wood such as the support timbers for a deck. Carpenters have that main nest and transport their pupae to a drier site, such as a house, shed, or garage, where they will become adults.

Then, hire a pest control company to treat that main nest; the house; and finally remove/replace the infested wood in your structure.

See this info from Cornell:

http://idl.entomology.cornell.edu/files/2013/11/Carpenter-Ants-21el62a.pdf

Thanks for all the advices. This year, i only see them for about three days and they were gone before i had a chance to buy the trap. But I have traps in place just in case.

The ant size is not as big as half an inches. They came from ground floor closet that have wood covering for heating pipes. I will rip the wood and inspect.

Kate