The Dance Construction Company-Washington's most daringly offbeat dance troupe-brought two offerings to its weekend concerts at the Marvin Theatre: a revised version of "Phase Tracing," first seen last fall, and the new "Catching Butterflies and Other Things that Move," both choreographed by the group under the supervision of director Maida Withers.

The rewards were concrete but spotty-privileged moments of arresting design popping up erratically amidst otherwise labored or inert surroundings.

"Phase Tracing" is the more ambitious of the two pieces, strongly suggesting the Merce Cunningham esthetic in its sculptural, exploratory movement style, its decor of silvered, hanging Mylar strips through which the dancers sporadically make passage, and its special microphone pick-ups which detect and respond to the dancers' comings and goings (Cunningham used something similar in his "Variations V").

Like a flock of gulls, the dancers wing from tight to widespread formationgs and back, and sometimes ripples of movement spread from one to the next by contagion. Yet even in its revived version, the work seems far too protracted, in the absence of a visible commanding structure.

"Catching Butterflies" is more playful, extracting eccentric variations from a single, minute-long phrase, to the accompaniment of a wan, wayward bass clarinet solo. It's more compact too, but still elusive in focus.