Leconectes striatellus, (LeConte, 1852)

Alarie, Yves & Michat, Mariano C., 2025, Testing the monophyly of the subtribe Deronectina and the phylogenetic position of the Nearctic endemic genus Leconectes Fery & Ribera, 2018 (Coleoptera: Dytiscidae, Hydroporinae) based on larval morphology, Zootaxa 5646 (2), pp. 255-274 : 259-264

Description of larvae of L. striatellus (LeConte, 1852)

( Figs 1–14 , 16–21 )

Source of material. The larvae studied were reared ex ovo from adults ( Fig. 15 ) collected at the following localities:

Canada: British Columbia. Duteau Creek ca. 5 km west Lumby at Hwy 6, 31.v.1992, three instar III. Y. Alarie leg. USA: Oregon. Curry Co.: Mussel Creek, 4 km north of Ophir at Hwy 101, 25.iv.1991, one instar III. Y. Alarie leg. USA: New Mexico. Gila Co.: Mimbres River at Hwy 61, ca. 12 km east of Hwy 180, 30.iii.1998, three instar I; Bear creek at Hwy 211, 31.iii1998, one instar I, two instar II. Y. Alarie leg. USA: Arizona. Pima Co.: Santa Catalina Mountains, Mount Lemmon, Marshall Gultch Picnic area, 2,283 m elevation, 01.v.1997, two instar I, three instar III. Y. Alarie leg. USA: California. Orange Co.: San Juan Creek at State Route 74, 15.iii.2000, one instar I, one instar II, one instar III. Y. Alarie leg. USA: California. Monterey Co.: Carmel River off Cachagua Road , 14.iii.2001, one instar I, three instar II, three instar III. Y. Alarie leg.

Description, instar I ( Figs 1–14 )

Color: Body greyish black except anterior portion of frontoclypeus, A2 and proximal third of A3 creamy white to pale grey.

Body: Fusiform, narrow. Measurements and ratios that characterize the body shape are shown in Table 2 .

Head ( Figs 1–9 ): Head capsule ( Figs 1–2 ) pear-shaped, longer than broad, maximum width posterior to stemmata at about level of occipital suture, with neck constriction distinctly delimited; ecdysial line well marked, coronal line short; occipital foramen broadly emarginate ventrally; frontoclypeus bluntly rounded, lateral margin of nasale straight along posterior half; dorsal surface with two egg bursters; ventroapical margin of frontoclypeus with 14–16 spatulate setae [= lamellae clypeales of Bertrand (1972)], not interrupted medially; gular suture not visible; ocularium present, stemmata not visible ventrally; tentorial pits visible medioventrally. Antenna ( Figs 3–4 ) elongate, four-segmented, slightly shorter than HW; A1 the shortest, A3 the longest, with a ventroapical spinula; A4 distinctly longer than A1, A3’ short. Mandible ( Fig. 5 ) falciform, curved inward and upward apically; mandibular channel present. Maxilla ( Figs 6–7 ) with cardo fused to stipes; stipes short, broad; galea and lacinia absent; MP elongate, three segmented, shorter than antenna, MP2 about as long as MP1, MP3 the shortest. Labium ( Figs 8–9 ) with prementum small, subquadrate to subtrapezoidal, slightly broader than long, with elongate lateral spinulae, anterior margin deeply sinuated medially; LP about as long as MP, two segmented, LP2 longer than LP1.

Thorax ( Figs 10–11 ): Pronotum trapezoidal dorsally, ovate laterally, widest at posterior margin; subequal to meso- and metanotum combined; pronotum without transverse carina; both meso- and metathoracic terga with an anterotransverse carina; sagittal line visible on the three tergites; thoracic sterna membranous; spiracle absent. Legs ( Figs 10–11 ): long, composed of six segments (including pretarsus), L1 the shortest, L3 the longest; CO robust, elongate, TR divided into two parts, FE, TI and TA slender, subcylindrical; pretarsus with two long, slender, slightly curved claws, posterior claw shorter than anterior one on L1 and L2, claws subequal in length on L3; claws lacking basoventral spinulae; TI and TA with marginal elongate spinulae.

Abdomen ( Figs 12–14 ): Eight-segmented, segments I–VI sclerotized dorsally, membranous ventrally; segment VII sclerotized both dorsally and ventrally, ventral sclerite demarcated from dorsal one; tergites I–VII narrow, transverse, rounded laterally, without sagittal line, with anterotransverse carina, with long setae along lateral and posterior margins; spiracles absent on segments I–VII; segment VIII (= LAS) ( Figs 12–13 ) short, subtrapezoidal, lateral margins slightly converging from base to point of insertion of urogomphi, abruptly converging thereafter, completely sclerotized, ring-like, with anterotransverse carina dorsally and laterally; siphon short, bluntly rounded to acute apically. Urogomphus ( Fig. 14 ) elongate, two-segmented; U1 much longer than LAS and U2, non-sclerotized annulus at level of seta UR4.

Chaetotaxy ( Figs 1–14 ): Similar to that of generalized Hydroporinae larva (Alarie & Harper 1990; Alarie et al. 1990; Alarie 1991; Alarie & Michat 2007b) except for the following features: pores PAd, PAe, PAk and ANf and seta MX 4 absent; seta PA3 elongate, much longer than setae PA1 and PA2 ( Fig. 1 ); A4 with one additional pore ( Fig. 3 ); coxae and femora with a variable number of additional setae ( Figs 10–11 ; Table 3 ); setae UR2 and UR3 contiguously articulated, seta UR4 articulated posteriorly; setae UR5, UR6 and UR7 elongate and hair-like; seta UR8 inserted subapically; one additional pore present on urogomphomere 1 ( Fig. 14 ).

Numbers between slash marks refer to pro-, meso- and metathoracic leg, respectively

Description, instar II

As instar I except as follows:

Color: frontoclypeus predominantly yellow to pale brown, piceous black along anterior margin and with piceous black maculae over basal half; parietal piceous black, yellowish around ocularium; head appendages creamy white to pale yellow except A1, A4, distal half of A3, distal half of MP2, MP3 and distal half of LP2 piceous black; protergum predominantly yellow with a piceous black longitudinal stripe on each side; mesotergum broadly piceous mesally, yellow laterally; metatergum predominantly piceous with small yellowish maculae anterolaterally; legs piceous; abdomen: terga I–II yellow mesally, piceous black laterally; terga III–IV predominantly yellow with few piceous maculae: terga V–VI piceous black, tergum VII yellow, tergum VIII yellow anteriorly, broadly black posteriorly; urogomphi dark yellow proximally, becoming gradually black distally.

Body: Measurements and ratios that characterize the body shape are shown in Table 2 .

Head: Frontoclypeus lacking egg bursters; ventroapical margin of frontoclypeus with 20–25 spatulate setae. Antenna distinctly shorter than HW; A1 the shortest, A3 the longest, A4 slightly shorter than A1. Maxilla. MP slightly shorter than antenna, MP2 about as long as MP1. Labium. LP shorter than MP, LP2 as long as LP1.

Abdomen: Segment VII completely sclerotized, ring-like. Urogomphomere I with several non-sclerotized annuli (as in Fig. 19 ).

Chaetotaxy: Head capsule with numerous secondary setae; lateroventral margin of PA with 7–8 spine-like secondary setae; MN with one hair-like secondary seta on basoexternal margin; thoracic and abdominal sclerites I–VIII with numerous secondary setae; natatory setae present on dorsal margin of femora, tibiae, and tarsi (as in Fig. 21 ); secondary leg setation detailed in Table 4 ; U with several spiniform and hair-like secondary setae (as in Fig. 19 ).

Description, instar III ( Figs 16–21 )

As instar II except as follows:

Color ( Fig. 16 ): Parietal generally piceous black, sometimes white to pale yellow except for a V-shaped blackish macula along the ecdysial suture extending over occipital region; head appendages predominantly creamy white to pale yellow except A4, apex of A3, MP3, apex of MP2, and apex of LP2 black; protergum pale yellow with blackish maculae over anterior half; mesotergum greyish black with a lateral yellow stripe on each side; metatergum predominantly greyish black, with a median yellowish to pale brown macula; legs creamy white to pale yellow, femur, tibia and tarsus lightly infuscate; abdomen: terga I–II greyish black with a broad yellow-brown macula mesally; terga III–IV predominantly yellow to pale brown with few scattered piceous maculae; terga V–VI greyish black; tergum VII creamy white; tergum VIII greyish black, creamy white along lateral margin; urogomphomere I yellow proximally, gradually greyish black distally; urogomphomere II black.

Body: Measurements and ratios that characterize the body shape are shown in Table 2 .

Head ( Fig. 17 ): Ventroapical margin of frontoclypeus with 32–40 spatulate setae. Antenna: A4 half as long as A1. Maxilla. MP about as long as antenna, MP2 shorter than MP1. Labium. LP2 shorter than LP1.

Thorax ( Figs 16 , 20–21 ): Mesothorax with a spiracular opening on each side.

Abdomen ( Figs 16 , 18–19 ): Mesopleural region of segments I–VII with a spiracular opening on each side.

Chaetotaxy: lateroventral margin of PA with 9–12 secondary spine-like setae ( Fig. 17 ); secondary leg setation detailed in Table 4 and Figs 20–21 .

Ecology: Adult specimens of Leconectes striatellus ( Fig. 15 ) were collected from quiet sections of small creeks to small rivers. The species is known to be found as well along margins of lakes with sand and gravel bed ( Larson et al. 2000).

Distribution: Leconectes striatellus is distributed throughout much of western North America from the Canadian province Manitoba to the Pacific and from central Mexico to the Yukon Territory ( Larson et al. 2000).

Figures

FIGURES 1–2. Leconectes striatellus (LeConte, 1852), instar I: 1. cephalic capsule, dorsal aspect; 2. cephalic capsule, ventral aspect. EB, egg bursters; FR, frontoclypeus; LC, lamellae clypeales; PA, parietale; TP, tentorial pits. Numbers and lowercase letters refer to primary setae and pores, respectively. Color pattern not represented. Scale bar = 0.1 mm.

FIGURES 3–9. Leconectes striatellus (LeConte, 1852), instar I: 3. antenna, dorsal aspect; 4. antenna, ventral aspect; 5. mandible, dorsal aspect; 6. maxilla, dorsal aspect; 7. maxilla, ventral aspect; 8. labium, dorsal aspect; 9. labium, ventral aspect; A3’, lateral elongation of antennomere 3; AN, antenna; gAN, antennal group; LA, labium: gLA, labial group; MN, mandible: MX, maxilla; gMX, maxillary group; sp, spinula. Numbers and lowercase letters refer to primary setae and pores, respectively; *, additional pore. Scale bars = 0.1 mm.

FIGURES 10–14. Leconectes striatellus (LeConte, 1852), instar I: 10. metathoracic leg, anterior surface; 11. metathoracic leg, posterior surface; 12. abdominal segment VIII, dorsal aspect; 14. abdominal segment VIII, ventral aspect; 14. urogomphus, dorsal aspect. AB, abdominal segment VIII; CO, coxa; FE, femur; PT, pretarsus; TA, tarsus; TI, tibia; TR, trochanter; UR, urogomphus. Numbers and lowercase letters refer to primary setae and pores, respectively. Scale bars = 0.1 mm.

FIGURES 15–16. Leconectes striatellus (LeConte, 1852): 15. adult habitus, dorsal aspect; 16. instar III habitus, dorsal aspect (35 years alcohol preserved specimen). Scale bars = 1 mm.

FIGURES 17–19. Leconectes striatellus (LeConte, 1852), instar III: 17. head capsule, dorsal aspect; 18. abdominal segment VIII, dorsal aspect; 19. urogomphus, dorsal aspect. Scale bars = 0.2 mm.

FIGURES 20–21. Leconectes striatellus (LeConte, 1852), instar III: 20. metathoracic leg, anterior surface; 21. metathoracic leg, posterior surface. Scale bar = 0.2 mm.