Extracted from THE POLLEN-COLLECTING BEES OF THE ANTHIDIINI OF CALIFORNIA (Hymenoptera: Megachilidae) by Grigarick A., A. (1968).
The variation found in this species appears mainly as extent of maculation, although the usual bright yellow is somewhat paler on one male from Mt. Diablo. The color patterns from the males of the northern end of the Sierra Nevada Range are ger.-erally the most reduced. The yellow pattern enlarges further south and west, with the Coast Range speciŽmens being the most heavily maculated, although an occasional exception is noted. D. plenum closely resembles pudicum and dubium in both sexes. The male is best separated by the broad, rounded appearŽance of the apex of the penis valve (fig. 146) and sternum VI (fig. 145). The cutting edge of the manŽdible of the female is straight in plenum (fig. 175) and pudicum (fig. 176), but curved in dubium (tz. 185). The shape, color pattern, and presence (plenurr.. fig. 193) or absence (pudicum, fig. 191) of a fain:. median, longitudinal carina on tergum VI of the female separates these species. The close similarity of the females of these three species has led to the naming of two subspecies of plenum, one each belongŽing to pudicum and dubium.
This montane species is found predominantly :n California, although a few collections have been made in southern Oregon and western Nevada. It is d:stributed in the Coast, Cascade, and Sierra Nevada ranges in northern California and extends as far south aS Tulare County in the Sierra Nevada. Forty-six males and 22 females were observed. Biological information on plenum is limited to the rearing of one male and three females from a resin and gravel nest (fig. 225) by P. D. Hurd. The nest was conŽstructed on a branch at Ryan Creek, Mendocino County.
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