Baliosus californicus (Horn)

(Figs. 3, 27–31, 127)

Reared specimens. CALIFORNIA: El Dorado Co., Pony Express trail, 38.767044, -120.326003, 22.vii.2023, em. 2–15.viii.2023, C.S. &A.B. Eiseman & J.A. Blyth, ex Ceanothus integerrimus, # CSE8346 (8 adults, MLBM); Placer Co., Mosquito Ridge Rd., 9.vii.2018, em. 24–28.vii.2018, E. LoPresti, ex Ceanothus integerrimus, # CSE4842 (5 adults, MLBM) .

Photographed mine. CALIFORNIA: San Diego Co., Cleveland National Forest, 32.89513, -116.44807, 29.viii.2024, D.J. Ringer, Ceanothus palmeri (iNat 239729763) .

Hosts. Rhamnaceae: Ceanothus fendleri A.Gray, C. integerrimus Hook. & Arn., C. *palmeri Trel., C. velutinus Douglas ex Hook. (Chittenden 1902; Jones & Brisley 1925; Eiseman 2014). Adults have also been associated with C. leucodermis Greene (Clark et al. 2004) .

Biology. Eiseman (2014) examined two mines on C. velutinus and noted that each began with a small, ragged hole chewed well away from the leaf margin, with no egg remains evident. When completed, the mines covered 1.5– 2 cm 2 and each had the frass deposited in a mass of fine particles concentrated toward the center. On C. integerrimus, some of the mines began with a similar hole and some did not, but all had the egg deposited in a pit chewed on the lower surface and partially covered with dark brown excrement (Figs. 3, 27–31). Early mines were distinctly upper-surface rather than full-depth, initially appearing green from above and then becoming whitish. Frass was initially deposited in a central mass, later becoming more scattered but still concentrated centrally.

Parasitoids. Chittenden (1902) noted that an unspecified chalcidid had been reared from the larvae of this species mining leaves of Ceanothus integerrimus . We reared an undetermined eulophine eulophid (CSE8331, CNC / iNat 202988548) from a collection of leaves of the same host that were mostly mined by Baliosus californicus, although there was a small number of Brachycoryna hardyi (Crotch) mines mixed in and we did not confirm which mine was the source of the wasp.