Thank you for reaching out and for sending photos.

Ant populations can fluctuate year-to-year due to various factors and new ants may discover new areas for nesting that they did not seek out in previous years. Based on your photos it looks like they had a nest somewhere in your basement stairwell that was disturbed and now they are relocating as seen by them carrying and moving the white/pale immature ants.

If they produce a rotten odor when crushed they could be what are commonly known as odorous house ants (Tapinoma sessile). Not all ant baits are equally effective and it can help to figure out what type of ants they are, which may need to be done by a pest control professional that can visit and collect samples; as some species are more sweet-loving than others (prefer sweet-loving geared baits). Baits containing hydramethylnon, fipronil or boric acid are slower acting and do not kill the workers before they have had a chance to share the baits with the queen and developing immature ants. 

You may already be doing this, but baits will need to be replaced and it could take 2+ weeks of baits to impact the nest. Follow bait label directions to know how often they need to be replaced. Cornstarch is more of a home remedy, which we do not recommend as it hasn't be scientifically tested or designed for pest control purposes. We haven't seen any science-based resource on the effectiveness of household cornstarch for managing ants so we can't speak to its use.

If this issue continues we would recommend contacting a professional pest control company. Companies that are members of the Maryland Pest Control Association and the National Pest Management Association have access to all current treatment practices. You can check a company's reputation by calling the Better Business Bureau. Ensure that the company has an active certification license from the Maryland Department of Agriculture Pesticide Regulation Section.

Some other helpful resources about managing ants:

• https://extension.usu.edu/planthealth/structural-and-nuisance/files/pest-id-handbook/Ants_2012_IPM_Manual.pdf
• https://extension.umd.edu/resource/ants-indoor-insects/