The ancestral stock from which A. opacus developed in Micronesia seemingly reached the area from Melanesia.
It has a brown iris, and the immatures lack the streaked underparts which are characteristic of A. opacus and other species.
The structure of its wing resembles that of A. opacus, but the primaries are more rounded.
Niger opacus lvis, clypeo emarginato, thorace postice rotundato, elytrorum lateribus humeralibus haud incisis.
opacus denotes shady, with reference to a pleasant and beneficial coolness, in opp.