Time was, seaside restaurants would put out a simple handwritten sign, usually around Memorial Day. It would say, “we have soft crabs,” and diners would line up for the fried favorite, served between two pieces of white bread.

Nowadays, the sign would have to stay up much of the year. Thanks to increased demand, better shipping methods, a changing global palette and a drive for artisanal and local food items, the proverbial “bug on a bun” has been elevated to a place on top of salads, small plates and platters — and even cooking shows.

“It’s just getting unbelievable,” said Terry Vincent, owner of Lindy’s Seafood, a Hooper’s Island wholesaler that sells crabs from the Chesapeake Bay as well as from Florida, Georgia and North Carolina. “I think it’s like with oysters. Women are eating more oysters now. Women have come out of their shell for soft crabs. The demand is through the roof.”

Bill Addison, restaurant editor and roving critic for the popular website Eater, said that he sees soft crabs on menus around the country, mostly as a seasonal delicacy, and, he said, “usually offered in a fancier context than a sandwich, more like pan-fried and served with aioli or other complementary sauce.”

In the Bay, blue crabs generally shed en masse twice a year — in May and again in September or October. But crabs elsewhere have their own shedding runs, and at least some shedding goes on everywhere throughout the summer. That helps eateries keep up with demand.

“They may not always be from here, but we always have them to sell,” said Doug Wetzel, a chef at Gertrude’s in Baltimore. When Wetzel competed on the cooking show Chopped earlier this year, he and the other three contestants had to make an appetizer out of a soft-shell crab. He was the only one who knew what to do with it, he said.

At Coveside Crabs in Dundalk, Lee Carrion said she has soft crabs “from May until I can’t take them anymore.” She instructs customers how to prepare them at home: clean only right before you cook, and she recommends grilling them — not frying — to maximum buttery softness.

Ekiben, a steamed bun restaurant in Fell’s Point, caused something of a craze earlier this summer when it announced a soft-shell sandwich; And Halethorpe caterer Craig Falk started a soft-shell food truck, called Mr. Softy. He also had a pop-up restaurant in R. House, a new Baltimore food marketplace.

“To be very honest, I think something physiologically happens to Marylanders in the spring,” Falk said. “We’re thinking about crabs, the beach, the Shore. Soft shell crabs are the start of that summer season, with us mentally.”