That most reliable harbinger of summer, the group show, has arrived in galleries. The good news is, this old standard has had to reinvent itself. You'll rarely find the laundry list of gallery artists in a summer group show anymore, except with a large number of unaffiliated artists mixed in. Who knows? You may not encounter a single gallery artist.

You won't find any of the usual suspects in Pentimenti Gallery's "Think Global, Go Local," for example, because the Old City gallery's owner and director, Christine Pfister, was specifically looking for local artists whose work she had not previously exhibited. She found the six she eventually chose (and whose practices fit her theme - the importance of an environment to its inhabitants) by placing a call for entry at the Institute of Contemporary Art, the Center for Emerging Visual Artists, InLiquid, and the Leeway Foundation. One artist who responded to the call had shown with Pfister some time ago, but made the director's final cut.

The most unexpected interpretation of the show's theme are Piper Brett's sinuous sculptures of thin, bent Plexiglas strips of red or white that penetrate a wall through a mere sliver of space (imagine the rectangular space into which you slip your ATM card, but wider) and manage to make equally powerful use of both sides of the wall, as if they were two separate sculptures.

Our contemporary global connective tissue of cell phones and the Internet is evoked by EJ Herczyk's monumentally scaled multi-panel Avalanche, of digital prints painted with serpentine strokes of transparent black. The images in his much smaller multi-panel Cluster pieces suggest views of urban landscapes that could be put together to form a whole, like a jigsaw puzzle.

Alexis Granwell looks at structures as creators of psychological connections. Her etchings on mulberry paper look like diagrams or aerial maps formed from pinpricks, while the materials that compose her small wall sculptures - cast paper, cardboard, latex paint, and found objects - could be detritus from a wrecked building, rescued and sublimely transformed.

The gallery's small "project room" turns out to be the perfect environment for an eerily lit windowless wall of reclaimed vinyl siding and plywood by the architect-artist team of Jason Austin + Aleksandr Mergold, which seems to be a meditation on Levittown and other postwar developments that evolved from a choice for separation over assimilation.

Gloria Houng's work is clearly driven by environmental and ecological issues and is the most literal interpretation of the show's theme. Cast-wax rabbits, lined up in a row and colored in order from bright red to pale pink, made me think of Easter chocolates, wax candy lips, a population growth warning, and animal testing. They're simultaneously tempting and repulsive, local and global, with some dark humor thrown in. Though more physically delicate, her ominous vellum-over-paper pieces that depict layers of painted images of trees, telephone poles, and factory towers are more heavy-handed manifestations of her ideas.

Pentimenti Gallery, 145 N. 2nd St., 11 a.m. to 5 p.m. Wednesdays through Fridays, 12 to 5 p.m. Saturdays. 215-625-9990 or www.pentimenti.com. Through July 18

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Group hug

On Washington Square, meanwhile, Bridgette Mayer has assembled a sprawling do-gooder benefiting the nonprofit Back on My Feet, an organization that promotes the self-sufficiency of Philadelphia's homeless population by engaging homeless individuals in running as a means to build confidence, strength, and self-esteem. While not stringent on the gallery artist front - too many of her regulars are here - this summer group show of 100 donated works also boasts contributions from Back on My Feet participants and by such well-known Philadelphia artists as Candy Depew, Tristin Lowe, Eileen Neff, and Odili Donald Odita.

Some of the standouts are by the aforementioned, predictably, but also by Mark Brosseau, Jon Manteau, Tim McFarlane, J. McAleer, David Slovic, Brooke Steytler, Paul Santoleri, Rebecca Saylor-Sack, Ivan Stojakovic, and Jackie Tileston.

All works are priced between $500 and $1,000, and proceeds will directly benefit Back on My Feet.

Bridgette Mayer Gallery, 709 Walnut St., 10 a.m. to 6 p.m. Tuesdays through Saturdays. 215-413-8893 or www.mayerartconsultants.com. Through July 31.