Extracted from: Grigarick A.A., & Stange L.A., (1968). The Pollen Collecting Bees of the Anthidiini of California (Hymenoptera: Megachilidae) Bulletin of the California Insect Survey Volume 9.
Trachusa gummifera Thorp, 1963. Pan-Pac. Ent, 39(1):S6, 9, $. Holotype 9, Carson Ridge, Marin County, California (CAS).
Geographic range.—Central California Coast Range.
California records.—MARIN Co.: Carson Ridge, 1 $,2 9, V-30-59 (C. O'Brien, J. Powers, SS); 4 $, 31 9, VI-II-60 (J. Lawrence, J. Powers, CAS, CIS, SS); 3 9, VI-15-62, at nest site (P. Hurd, R. Thorp, CIS, RT); 2 9, VI-30-62 (R. Thorp, RT). SAN FRANCISCO Co.: San Francisco, 1 9, VI-22-S7 (D. Rentz, SS).
The species is black except for the cream-colored maculation of the clypeus of the male. This mark covers approximately the anterior two-thirds of the clypeus and extends on the median line to the frons. The heavy pubscence is whitish except for a reddish cast to that of the scutum and vertex.
Both sexes are separated from perdita by having the third segment of the labial palpus longer than the fourth, whereas they are subequal in perdita. Tergum VII of the male of gummifera (fig. 130) is without the median, platelike extension of the apex as in perdita. The sixth tergum of the female of gummifera has a basal elevation that is medially emarginate (fig. 131), but this area is a produced median fold in perdita.
T. gummifera is infrequently collected: only 5 males and 39 females have been observed and these have been limited to the area west of San Francisco Bay.
Unpublished observations by Thorp indicate a similarity of nesting habits to those of perdita, but they differ in a number of respects; for instance, the nest entrance of gummifera was associated with a tumulus and some tunnels were branched (fig. 212) one or several times.