|scientific name Synaxis pallulata |
common name September Thorn
Montane coniferous forest.
Adults fly from August to October in BC (Jones 1951); no Alberta data available.
The September Thorn, like several other large geometrids that fly in the fall, is bright rust-brown or yellowish. The discal spots are small and black but distinct; wings with a pointed protrusion at mid-margin.
Similar to the extremely variable Prochoerodes trnasversata, but the PM line joins the wing margin in a straight line, whereas it angles sharply toward the thorax near the apex in transversata. Synaxis jubararia is very similar, but pallulata has heavier crosslines with more dark mottling. No structural differences between jubararia and pallulata are known.
The mature larva is marbled brown and dark grey, with a faint herringbone pattern dorsally; there are two other larval colour morphs, one cream-green the other brown. Pupation is in the upper soil layers, and the egg presumably overwinters (Duncan 2003).
Not of concern.
Larvae feed primarily on Douglas-fir (Pseudotsuga) and hemlock (Tsuga), and occasionally on spruce (Picea), fir (Abies), and lodgepole pine (Pinus contorta) (Prentice 1963).
BC and western Alberta south to Oregon (McGuffin 1987).
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