Sen. Susan Collins at a 2011 news conference in Washington, DC. Alex Wong/Getty Images

Republican Sen. Susan Collins of Maine was caught on a hot mic Tuesday calling Republican Rep. Blake Farenthold of Texas "unattractive" during a legislative session Tuesday morning.

Last week, Farenthold singled out "female senators from the Northeast" as being responsible for hampering the Senate's effort to repeal and replace the Affordable Care Act, the healthcare law better known as Obamacare.

Collins, along with Republican Sens. Shelley Moore Capito of West Virginia and Lisa Murkowski of Alaska, has opposed the Senate's proposed healthcare overhaul.

Farenthold said "if it was a guy from south Texas" opposing the legislation, "I might ask him to step outside and settle this Aaron Burr-style."

Collins mentioned Farenthold's comments Tuesday morning while speaking with a male senator during a subcommittee hearing.

"Did you see the one who challenged me to a duel?" Collins asked her colleague.

"I know," he replied. "Trust me — you know why he challenged you to a duel? Because you could beat the s--- out of him."

Collins laughed and added, "He is so unattractive, it's unbelievable."

She later asked her colleague, "Did you see the picture of him in his pajamas next to this bunny?" before the microphone cut off.

Collins was most likely referring to this photo:

The other senator wasn't immediately identified, but many reporters on Twitter speculated it was Sen. Jack Reed, the ranking Democratic member of the subcommittee.