Since 1981, Momix dancer-illusionists have been twisting, bending and shape-shifting in works defying physical boundaries and inventiveness. This Connecticut troupe founded by choreographer Moses Pendleton is returning to Hancher with “Opus Cactus,” grounded in the life and landscape of the American southwest. Created as a 20-minute piece in 2001, “Opus Cactus” has been transformed into a full-length work full of cactuses, slithering lizards and fire dancers. Clive Barnes of the New York Post said: “ ... Pendleton’s ingenuity, theatricality and cunning imagination are seen at full stretch in strange vignettes of the Sonoran desert.”