CHICAGO, Sept 25 (Reuters) - An eclectic blues musician, an artist who draws on barrels and a biologist who studies spider silks were among 24 scholars, scientists and artists given no-strings $500,000 "genius" grants, a foundation announced on Tuesday.

The Chicago-based MacArthur Foundation determines in secret through a changing cast of nominators who receives the five-year grants, awarded since 1981, and its "Fellows" can spend the money any way they wish.

"With the gift of time and unfettered opportunity to create and explore, we are confident that the Fellows will follow their hearts and their minds wherever they lead, making new discoveries and making a difference in the world," foundation President Jonathan Fanton said in a statement.

Some of the awardees:

- Musician Corey Harris, of Charlottesville, Virginia, weaves together traditional Delta blues with elements from jazz, reggae, gospel, and African and Caribbean folk music, the foundation said.

- Artist Whitfield Lovell of New York City meticulously renders life-sized portraits of obscure figures on wooden walls, fences or barrels and includes found objects such as frying pans, bed frames and clocks in his installations, which evoke the evolution of civil rights.

- Cheryl Hayashi, a biologist at the University of California in Riverside, examines the silks spun by spiders and caterpillars, with potential applications from biodegradable fishing line to sutures.

- Chicago-born writer Stuart Dybek was praised for short stories that resemble parables, whose characters' dream-lives contrast with their stifling urban surroundings.

- Forensic anthropologist Mercedes Doretti, of New York and Buenos Aires, has unearthed evidence of "crimes against humanity" in more than 30 countries, starting with those who "disappeared" during Argentina's military dictatorship.

- Deborah Bial, through her Posse Foundation in New York, developed a rigorous assessment and tutoring program for teenagers who might otherwise stand little chance of going to college.

- Inventor Saul Griffith of Alameda, California, holds patents in optics, nanotechnology and textiles -- with many of his creations benefiting children.

- Sven Haakanson, of Kodiak, Alaska, is an anthropologist and museum director and a driving force in preserving North American native culture, especially his native Alutiiq.

- Civil engineer Marc Edwards, of Virginia Polytechnic Institute and State University in Blacksburg, analyzes urban drinking water and works on ways of removing lead and other contamination.

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