Octotoma marginicollis Horn

Eiseman, Charles S., 2014, New Host Records and Other Notes on North American Leaf-Mining Chrysomelidae (Coleoptera), The Coleopterists Bulletin 68 (3), pp. 351-359 : 354

Octotoma marginicollis Horn

In Madera Canyon on 6 November 2012, I encountered adults of this species feeding on B. betonicifolia , creating networks of wavy-edged, skeletonized patches on the surfaces of the leaves. In the vicinity of the adults were several full-depth blotch mines that followed the leaf edges ( Fig. 8 ). In contrast to the leaf mine on this plant discussed under M. rubrolineata , in these the frass was fairly sparse and consisted of compact pellets 1–2 times as long as wide. This would be atypical frass for a chrysomelid leafminer, but the short, squat larvae shown in my backlit photographs ( Fig. 8 ) of the mines (solitary larvae in two leaves, and four larvae in a third) are shaped more like beetle than moth or sawfly larvae, and the lack of visible legs is consistent with Octotoma Dejean (Ford and Cavey 1985) . However, I failed both to rear the larvae and to save their remains, so I cannot confirm Brickellia as a larval host for this beetle either. The only known larval host of O. marginicollis is Perezia thurberi (A. Gray) Reveal & King (Asteraceae) , in which the leaves are said often to be completely mined out by several larvae whose mines have become confluent (Jones and Brisley 1925). Other existing descriptions of Octotoma leaf mines suggest that mine shape and frass deposition can vary from species to species. Octotoma plicatula (F.) forms tentiform mines in Campsis radicans L. ( Bignoniaceae ), with excrement accumulating as a black spot near the base of the leaf; Octotoma championi Baly makes a very narrow mine in Lantana spp. (Verbenaceae) , with a very faint fecal trail ( Staines 1989); and Octotoma scabripennis Guérin-Méneville , also on Lantana , produces a blotch mine with a central dark colored area and several radiating feeding galleries ( Harley 1969; Broughton 1999).

Figures

Figs. 7–12. 7) Presumed mine of Microrhopala rubrolineata in Brickellia betonicifolia leaf; 8) Brickellia betonicifolia leaf with skeletonizing by adult Octotoma marginicollis. The mine along the leaf margin was possibly made by a larva of this species; 9) Hog-peanut (Amphicarpaea bracteata) leaf with mine of Odontota mundula overlapping mine of Leucanthiza amphicarpeaefoliella. The latter is visible as an indistinct band of frass in the lower left; 10) Mine of Odontota scapularis in groundnut leaf, with excrement-covered egg mass at right edge of photo; 11) Odontota scapularis egg mass containing pupae of parasitoid wasps; 12) Mine of Stenopodius texanus in Abutilon leaf.