The larvae of caddisfly species (Insecta, Trichoptera) in northern Thai streams and their relationships to environmental variables Author Seetapan, Kriengkrai 0000-0003-0900-6890 School ofAgricultureandNaturalResources, University ofPhayao, TumbolMaeka, MuangDistrict, PhayaoProvince, 56000, THAILAND kook 82 @ hotmail. com; https: // orcid. org / 0000 - 0003 - 0900 - 6890 kook82@hotmail.com Author Prommi, Taeng On 0000-0001-5160-8663 Faculty of Liberal Arts and Science, Kasetsart University, Kamphaeng Saen Campus, Nakhon Pathom Province, 73140, THAILAND faastop @ ku. ac. th; https: // orcid. org / 0000 - 0001 - 5160 - 8663 faastop@ku.ac.th text Zootaxa 2022 2022-12-21 5222 4 301 324 journal article 54549 10.11646/zootaxa.5222.4.1 87a69657-2f80-4f08-a802-19261351f311 1175-5326 7466720 242B3947-087C-40D5-8BE1-2C7C9C261650 Hydropsyche pallipenne Banks 1938 ( Figs 2–19 ) Larva: Total length 9.0–10.0 mm (n = 10). Overall body shape in alcohol generally as for other Hydropsychidae . Head yellow, except brown in posterolateral half of frontoclypeus. Thoracic nota yellow, each with lateral muscle scars ( Figs 2–4 ). Head: Head capsule length 0.88–0.97 mm ; width 0.82–0.85 mm . Dorsum of head yellow except brown on either side of frontoclypeus posteriorly, frontoclypeus with posterolateral half brown, triangular yellow mark anteriorly, and circular yellow mark posteromesally. Frontoclypeus with anterior margin broadly and shallowly concave, slightly crenulate, with dense fringe of short setae extending along anterior margin ( Figs 3, 5 ). Head with long, black, erect, truncate peg-like setae (tp) and acuminate peg-like setae (ap) on dorsal and lateral regions in anterior three-quarters ( Fig. 3 ). Frontoclypeus with same setae scattered in anterolateral corners only ( Figs 3, 5 ). Head ventrally yellow with darker brown pigmentation on pair of stridulatory surfaces; stridulatory files present ventrally near midlength ( Fig. 4 ). Labrum light-brown; elliptical in dorsal view; bearing well-developed, golden- to light-brown setae anterolaterally, pectinate setae and stout setae on anterior half of dorsal surface ( Fig. 6 ). Mandibles dark-brown with 2 apical and 3 mesal teeth, several long setae on lateral edges, left mandible with well-developed setal tuft mesally ( Figs 3, 4, 8 ). Submentum light-brown, with anteromesal cleft, anterolateral margins with long setae. Anterior ventral apotome broadly triangular, posterior ventral apotome very small, triangular ( Figs 4, 7 ). Thorax: Nota yellow with slightly darker muscle scars laterally; densely covered with long, erect, truncate peglike setae and tapered hair-like setae, these same setae projecting beyond anterior margin. Pronotum with muscle scars midway between midline and lateral margin in posterior half; meso- and metanota with muscle scars laterally ( Figs 9−11 ). Prosternite light brown, transverse, narrow, with fine, dark anterior margin and broad dark band along posterior margin; pair of large posterolateral sclerites each brown on submesal 2/3, yellow and brown on lateral 1/3 ( Fig. 12 ). Foretrochantins deeply forked, each with long, black setae on ventral fork ( Fig. 13 ). Forelegs each with numerous, feather-like setae on posterior surface of coxa; trochanter with feather-like setae on ventral margin; femur with row of long, dark, spike-like setae along ventral margin and short, dark, setae on external (posterior) surface ( Fig. 13 ). Mid- and hind legs similar in size, shape, and structure; with feather-like setae on posterior surfaces of trochanters and femora ( Figs 14−15 ). Mesosternum with one pair of gills and metasternum with 2 pairs of gills; gills each consisting of central stem bearing approximately 20 lateral filaments ( Fig. 2 ). Abdomen: Abdominal segments I–IX densely covered with slender, dark hair-like setae (hl) and triangular scale-like setae (sh) ( Figs 2 , 16–17 ). First sternum with 2 pairs of gills with adjacent bases. Segments II–V each with one pair of submedian ventral gills. Segments II–VII each with one pair of sublateral gills each arising from common base ( Figs 2 , 19 ). Sternum VIII with pair of small, triangular sclerites bearing spike-like setae ( Fig. 18 , arrows). Sternum IX with pair of large triangular sclerites bearing spike-like setae emanating from prominent sockets ( Fig. 18 , arrows). Tergum IX with pair of small lateral sclerites and pair of large subdorsal sclerites ( Fig. 19 , arrow on right large subdorsal sclerite). Anal prolegs with bent claw and cluster of long bristles; their lateral sclerites with long, black setae; each with fan of long setae subapicodorsally ( Figs 2 , 18, 19 ). FIGURES 2–8. Larva of Hydropsyche pallipenne Banks 1938: 2 , larval habitus, right lateral; 3, head, right dorsolateral; 4, head, ventral; 5, frontoclypeal apotome, dorsal; 6, labrum, dorsal; 7, submentum and anterior ventral apotome, ventral; 8, mandibles, ventral. ap = acuminate peg-like setae, tp = truncate peg-like setae. FIGURES 9–15. Larva of Hydropsyche pallipenne Banks 1938: 9 , pronotum, dorsal; 10, mesonotum, dorsal; 11, metanotum, dorsal; 12, prosternites, ventral; 13, right pleuron, foretrochantin, right foreleg, right posterolateral; 14, right midleg, right posterolateral; 15 right hind leg, right posterolateral. Material examined: THAILAND : PHAYAO PROVINCE : Wieng Lor Wildlife Sanctuary, Huai Mae Jun, 434 m a.s.l., 19°15'44.0"N , 100°08'31.2"E , 25-x-2019 , 12 larvae , 2 male pupae, 2 male adults, leg. Prommi; Phu Sang National Park , Nam Phuai Bon , 446 m a.s.l. , 19°39'55.8"N , 100°22'37.4"E , 23-i-2021 , 16 larvae , 4 male pupae, 3 male adults, leg. Prommi ; Nam Phuai Lang , 474 m a.s.l. , 19°40'27.9"N , 100°23'20.2"E , 24-i-2021 , 33 larvae , 5 male pupae, leg. Prommi ; Huai Pong Pha , 560 m a.s.l. , 19°42'12.2"N , 100°23'56.6"E , 24-ix-2021 , 18 larvae , 2 male pupae, 2 male adults, leg. Prommi ; Huai Sai Guad , 485 m a.s.l. , 19°43'52.6"N , 100°19'46.2"E , 25-ix-2021 , 10 larvae , 1 male adult, leg. Prommi ; Nam Yuan Ton , 510 m a.s.l. , 19°30'02.5"N , 100°27'01.6"E , 25-vi-2021 , 12 larvae , 3 male pupae, 1 male adult, leg. Prommi ; Nam Yuan Huai Pum , 495 m a.s.l. , 19°31'17.5"N , 100°24'25.0"E , 26-vi-2021 , 13 larvae , 2 male pupae, 2 male adults, leg. Prommi.