Metriocnemus erythranthei sp. nov. and Limnophyes viribus sp. nov. (Diptera: Chironomidae: Orthocladiinae): leafminers of monkeyflowers, speedwells, and other herbaceous plants, with new observations on the ecology and habitats of other leaf-mining Chironomidae Author Eiseman, Charles S. 0000-0001-5496-9114 ceiseman@gmail.com Author Namayandeh, Armin 0000-0003-2136-0497 arminnamayandeh@trentu.ca Author Linden, John Van Der 0000-0003-2651-0634 1815 Whitetail Rd., Decorah, IA 52101, U. S. A. johnbvdl @ gmail. com; https: // orcid. org / 0000 - 0003 - 2651 - 0634 johnbvdl@gmail.com Author Palmer, Michael W. 0000-0001-5496-9114 PBEE, Oklahoma State University, Stillwater, OK 74078, U. S. A. Current address: Department of Botany and Plant Biology, Oregon State University, Corvallis, OR 97311, U. S. A. mike. palmer @ okstate. edu; https: // orcid. org / 0000 - 0003 - 1452 - 2152 Corresponding author. arminnamayandeh @ trentu. ca ceiseman@gmail.com text Zootaxa 2023 2023-02-28 5249 1 41 68 http://dx.doi.org/10.11646/zootaxa.5249.1.3 journal article 10.11646/zootaxa.5249.1.3 1175-5326 7685232 6AD83534-E480-4CA2-99AE-785E25133F76 A key to the known fourth instar larval stages of North American Metriocnemus van der Wulp 1. Mentum with 4 small median teeth and 5 pairs of lateral teeth ( Epler 2001 : page 7.86, couplet 2(1’))................................................................................................... M. knabi Coquillett, 1904 - Mentum with bifid or simple median tooth and 4 to 5 pairs of lateral teeth........................................ 2 2. Mentum with simple median tooth and 5 pairs of lateral teeth ( Saether 1989 : Figure 12G )...... M. ursinus (Holmgren, 1869) - Mentum with bifid median tooth and 4 to 5 pairs of lateral teeth................................................ 3 3. Mentum with a wide bifid median tooth and 4 pairs of lateral teeth ( Fig. 3h )...................... M. erthranthei sp. nov. - Mentum with narrow bifid median tooth and 5 pairs of lateral teeth.............................................. 4 4. Median tooth of the mentum is comparatively small, sitting much lower than lateral teeth............................ 5 - Median tooth of the mentum comparatively well-developed, sitting slightly lower or higher than lateral teeth............ 6 5. Basal antennal segment no longer than wide ( Saether 1989 : Figure 12B ). Labral lamella and SI simple ( Saether 1989 : Fig. 12D ). Median tooth of mentum sunken ( Epler 2001 : page 7.86, couplet 3(2’); Orendt & Bendt 2021 : page 119, couplet D7; Saether 1989 : Fig. 12H ). Anal tubules long and slender ( Saether 1989 : Fig. 12J )..................... M. fuscipes (Meigen, 1818) - Basal antennal segment longer than wide ( Fig. 7b ). Labral lamella comb-like and SI trifid ( Fig. 5c ). Median tooth of mentum not sunken ( Fig. 7e ). Anal tubules short and wide ( Fig. 7f )......................................... M. sp. “ Oregon ” 6. Antenna 4 segmented ( Cranston & Judd 1987 : Fig. 4a ). Basal antennal segment L/W> 4. Median tooth of mentum stands higher than 1 st lateral teeth. Setae submenti aligned with the 3 rd lateral teeth of mentum ( Cranston & Judd 1987 : Fig. 4c )............................................................................ M. yaquina Cranston & Judd, 1987 - Not with the above combination of characters............................................................... 7 7. Abdominal segments with long setae, each half as long as the segment bearing it.................... M . sp. A Epler, 2001 - Abdominal segments without long setae................................................................... 8 8. Procercus as wide as long or wider than long.AR 1.7–1.8. Basal antennal segment L/W: 2.3 (Th. Bendt & H.K.M. Moller Pillot, in litt.)................................................................................ M. tristellus agg. * - Not with the above combination of characters............................................................... 9 9. Median bifid tooth of mentum as high as the 1 st lateral teeth ( Saether, 1989 : Fig. 6E ). Basal antennal segment L/ W 2.5 –2.6. Head length 0.44–0.45 mm ................................................................. M. brusti Saether, 1989 - Median bifid tooth of mentum clearly lower than 1 st lateral teeth. Basal antennal segment L/ W 1.1 –2.4. Head length 0.13–0.47 mm ............................................................................................... 10 10. Basal antennal segment L/ W 1.1 . AR 0.67. Mandible with 3 inner teeth ( Epler 2001 : page 7.162). Procercus with 4 anal setae.............................................................. M. sp. (= Orthocladiinae genus E, Epler, 2001 ) ** - Not with the above combination of characters.............................................................. 11 11. AR 1.5–1.8. Head length 0.28-0.31 mm ( Saether, 1989 )............................... M. albolineatus (Meigen, 1818) - AR 2.0–2.2. Head length 0.39–0.47 ( Saether, 1989 )................................ M. eurynotus (Holmgren, 1883) ***