After Brundin (1966):
Occipital margin forming a moderately pronounced neck possessing deep dorsolateral incisions. The lamellar S I of labrum inserting far laterad; S II and S III seta-like. The 5 lamellar teeth of the epipharyngeal comb arranged in a simple row. Labium with very broad middle tooth and 8 lateral teeth on each side gradually decreasing in size.
Reissmesa (called Araucania originally by Brundin, 1966, preoccupied) belongs to the Diamesinae tribe Heptagiini – the tribe is austral and well-defined in all stages. However it is not possible yet to distinguish the larvae to genus level with any confidence: too few have been reared and it is unclear which characters are reliable. Note that the ‘distinctive’ collar (occipital margin of the head) apparently is a feature only of final instar larvae.
For the described larva of Reissmesa valdesiana (the only associated larva in the genus) Brundin (1966) wrote:
Very similar to Paraheptagyia larva but differing in the following:
Head less elongate and more typically egg-shaped, a consequence of a much shorter ‘neck’ (collar). In lateral view the strongly sclerotised occipital margin is pronouncedly S-shaped and exhibiting a deep dorsolateral emargination. The dorsal and lateral setae of the head are comparatively short and stout. The flattened labral setae SI insert far laterad anterior to the SIV and near the chaetae. The basal rings of the SII and SIII are in near contact. The first lateral tooth of the mentum is fused with the middle tooth giving the appearance of a broad median tooth – the remaining 8 lateral teeth decrease evenly in size. The seta interna of the mandible is divided into 16 branches.
Three species are described, all from Andean Chile.
The holotype of Reissmesa antiqua comes from the shore of Lago Villarrica near the outflow of Rio Tolten in the Province of Cautin in southern Chile. Other specimens came from Rio Petrohué near Ensenada (Province Llanquihue), a mountain stream at Peulla hotel, Rio Canteras, Peulla area, and Cerro Rigi also near Peulla, and across the Andes in Argentina at Arroyo Nireco, Bariloche in Province Rio Negro.
The holotype of R. gelida is from a glacier torrent on Cerro Morado, 4300 m, Lo Valdes, Andes of Santiago in central Chile. Another specimen also came from Lo Valdes, from Rio Volcan at 2100 m.
The holotype of R. valdesiana is from a torrent near Refugio house also at Lo Valdes, Andes of Santiago at 2300 m.