Odontomesa fulva (Kieffer, 1919)

Namayandeh, Armin & Beresford, David V., 2017, New range extensions for the Canadian Chironomidae fauna from two urban streams, CHIRONOMUS Journal of Chironomidae Research 30 (30), pp. 76-80 : 76-77

Odontomesa fulva (Kieffer, 1919)

Larva (n=2). Figs. 1 a-g.

Description. Postmentum L=184.3-202.5 μm (194.3 μm). Antenna 4 segmented ( Fig. 1a ), AR=2.0-2.4 (2.2). Labrum with S IV A and premandibles ( Fig. 1b ). Mentum ( Fig. 1c ). Posterior margin of ventromental plates more or less straight and parallel with anterior margin ( Fig. 1d ). Mandible with seta interna split into 3 segments ( Fig. 1e ); basal external seta of mandible splits into 2-8 setae from the base ( Fig. 1 e-f). Procercus well-sclerotized with 8 apical setae. 2 long anal setae are present ( Fig. 1g ). Posterior parapods 3X longer than wide ( Fig. 1g ). Four cone shaped anal tubules are present ( Fig. 1g ).

Notes. Larval stages of O. fulva and O. ferringtoni ( Saether 1986) were revised by Liu et al. (2016). A major distinguishing character for the larvae is the shape of the ventromental plates. As compared to O. ferringtoni , the posterior margin of the ventromental plate of O. fulva is straight and practically parallel with the anterior margin ( Liu et al. 2016). This contrasts Saether’s (1986) use of basal external setae characteristics to separate the two species. Additionally, Chinese specimens of O. fulva examined by Liu et al (2016) have a postmentum length of 180-200 μm, extending the range of 131-158 μm presented by Saether (1986); notably, the specimens discussed here have a postmentum length of 184.3-202.5 μm. The seta interna of the mandible splits into 3 segments in our specimens, corresponding with characteristics of larval O. fulva nearctica Saether, 1986 ; however, basal external setae of the mandible split into 2-8 branches as opposed to 12-23 branches for O. fulva nearctica reported by Liu et al. (2016).

Study sites. Bowmanville Creek, Bowmanville, Ontario; 43° 54’ 22.90” N 78° 41’ 12.8” W.

Ecology and habitats. Larvae inhabit shallow pools of rivers and streams, especially cold-water streams. This species is univoltine in its emergence phenology ( Phillips et al. 2013).

Nearctic distribution: Canada (Ontario, Saskatchewan, Yukon Territory?); USA (Florida, Georgia, Illinois, Maine, Michigan, Minnesota, Mississippi, Montana, New Mexico, North Carolina, Pennsylvania, South Carolina, Wisconsin).

Notes: According to Phillips et al. (2013), there are debates regarding the occurrence of this species in Canada. The CNC collected specimens by D.R. Oliver in 1990 and record O. fulva from Frankford, Kintor, and Trout creeks in southern Ontario. Additionally, a single specimen was collected in 1976 by K. Dance near Waterloo, Ontario ( Phillips et al. 2013). Report of the species from Yukon Territory is also not confirmed, although, Philips et al. (2013) report the species from this territory. Finding this species in Bowmanville Creek confirms the species’ occurrence in Ontario and extends its range from southern to more central regions of the province. The species has also a Palearctic distribution, as it is widespread in Europe and has been reported in Xinjiang Uygur Autonomous Region of the Palearctic China ( Liu et al. 2016).

Figures

Figure 1. Odontomesa fulva (Kieffer, 1919) larva. a) Antenna, b) Labrum, SIV A (black arrow) and premandibles (white arrows), c) Mentum, d) Ventromental plate, e) Mandible, arrow points to basal external seta with 2 branches at the base, f) Variation of basal external seta with several branches, g) Posterior portion of the larva.