Allomatus nannup Watts

Alarie, Yves & Watts, Chris H. S., 2003, Larval Morphology of Allomatus nannup Watts (Coleoptera: Adephaga: Dytiscidae), The Coleopterists Bulletin 57 (3), pp. 255-264 : 257-261

Larvae of Allomatus nannup Watts

( Figs. 1–6 )

Diagnostic Combination. Lateral lobes (¼ adnasalia) clearly delineated ( Fig. 1 ); lamellae clypeales conical ( Fig. 1 ); antenna shorter than HW; lateral elongation of antennomere 3 short, A39/A4, 0.20; mandible not toothed; primary pore ANg inserted proximally; setae AN2 and AN3 not articulated at same level on antennomere 3; prementum with 2 additional setae; head appendages with several spine-like secondary setae; metathoracic legs about 1.20 times as long as prothoracic legs, with additional spiniform setae on each article; tibiae not pseudo-chelate; spinulae on ventral margin of tibiae (lacking on metatibia) and tarsi spine-like ( Fig. 5 ); primary setae CO6 and CO7 inserted distally on procoxa; posterodorsal margin of tibiae with a row of additional natatory setae (1 st instar) ( Fig. 6 ); seta TI6 lacking on protibia, short and spine-like on mesotibia and hair-like on metatibia; trochanter with.15 secondary setae ( Table 2); last abdominal segment subtrapezoidal, truncate along posterior margin, with spine-like additional setae present (1 st instar); siphon faintly delineated ( Fig. 2 ); urogomphus longer than last abdominal segment, with additional setae (1 st instar) ( Fig. 2 ) and secondary setae (2 nd and 3 rd instar).

Description: 1 st Instar ( Fig. 1 ). Color. Head capsule predominantly yellow with some small brownish maculae laterally; head appendages predominantly pale yellow except articulation of A1 and A2, dark brown; thoracic and abdominal terga predominantly yellow with a few small dark brown maculae; legs and urogomphi predominantly yellow.

Head ( Fig. 1 ). HL ¼ 0.83–0.88 mm (mean ¼ 0.85 mm, n ¼ 6); HW ¼ 0.80–0.85 mm (mean ¼ 0.83 mm, n ¼ 6); FCL ¼ 0.40–0.46 mm (mean ¼ 0.44 mm, n ¼ 6). Cephalic capsule ( Fig. 1 ) obovate, about as long as broad (HL/HW ¼ 1.01–1.07), lateral lobes (¼ adnasalia) distinct; apical margin of frontoclypeus with 19–20 spatulate lamellae clypeales. Antenna slightly shorter than HW (length of antenna/ HW ¼ 0.89–0.95); A2. A3 » A4. A1, A2/A3 ¼ 1.06–1.20; A39/A4 ¼ 0.13–0.16. Mandible. Inner margin not toothed. Maxilla. Galea 0.71–0.73 times length of palpomere 1; length of MX 3/ length of MX 2 ¼ 1.27–1.28. Chaetotaxy and porotaxy. Parietals lacking additional setae; prementum with 2 additional setae; antennomere 4 lacking an additional pore; primary pore ANg inserted proximally; primary seta AN2 articulated distally, not at level of seta AN3. Legs ( Figs. 3–6 ). Tibiae of normal shape (i.e., not pseudo-chelate); metathoracic legs about 1.20 times length of prothoracic legs, and about 3.50 times HW; femur. coxa. tibia » tarsus. trochanter (metathoracic leg); spinulae on ventral margin of tibiae and tarsi spine-like and strongly developed, those on protarsus articulated on a black carina (visible under a dissecting microscope); longest of metathoracic claws 0.36–0.37 times as long as metatarsus. Chaetotaxy and porotaxy. Setae CO6 and CO7 inserted distally on all legs; seta FE6 hair-like on each femur; seta TI6 lacking on protibia, short and spine-like on mesotibia, and elongate and hair-like on metatibia. Additional setae present on each article ( Table 1). Abdomen ( Fig. 2 ). LLAS ¼ 0.43–0.50 mm (mean ¼ 0.46 mm, n ¼ 6). Segment 8 subtrapezoidal dorsally, shorter than HW, LLAS/HW ¼ 0.53–0.58, truncate posteriorly. Siphon faintly delineated. Urogomphus ( Fig. 2 ). Length of urogomphus ¼ 1.00– 1.02 mm (mean ¼ 1.01 mm, n ¼ 6), 2.02–2.39 times as long as LLAS, 1.18–1.27 times as long as HW. Chaetotaxy and porotaxy. Urogomphus with several additional spine-like setae.

2 nd Instar (Figs. cf. Alarie et al. 2001). Color. Head capsule predominantly yellow with a blotchy pattern comprising several large brownish maculae; head appendages predominantly pale yellow except A1 dark brown; thoracic and abdominal terga predominantly yellow with a blotchy pattern; legs creamy white to pale yellow; urogomphi predominantly yellow. Head. HL ¼ 1.32– 1.35 mm (mean ¼ 1.34, n ¼ 3); HW ¼ 1.18–1.23 mm (mean ¼ 1.21 mm, n ¼ 3); FCL ¼ 0.66 mm (mean ¼ 0.66 mm, n ¼ 3). Cephalic capsule obovate, slightly longer than broad (HL/HW ¼ 1.08–1.14), lateral lobes (¼ adnasalia) delineated; apical margin of frontoclypeus with 35–39 spatulate lamellae clypeales; parietals with 8–10 lateral spines. Antenna shorter than HW (length of antenna/ HW ¼ 0.77–0.80); A2. A1 subequal to A3. A4, A2/A3 ¼ 1.11–1.23; A39/A4 ¼ 0.11– 0.13. Mandible. Inner margin not toothed. Maxilla. Galea 0.63–0.71 times length of MX 1; length of MX 3/ length of MX 2 ¼ 0.92–1.09. Chaetotaxy and porotaxy. Prementum with 2 additional setae; primary pore ANg inserted proximally; primary seta AN2 articulated distally, not at level of seta AN3; head appendages with several secondary spine-like setae: antennomere 1 (7–10), antennomere 2 (9), maxillary palpomere 1 (7), maxillary palpomere 2 (6–7), labial palpomere 1 (10). Legs. Tibiae of normal shape (i.e., not pseudo-chelate); metathoracic legs about 1.20 times length of prothoracic legs, and about 3.50 times HW; femur. coxa. tibia » tarsus. trochanter (metathoracic leg); length of metafemur/length metacoxa about 1.20; longest of metathoracic claws 0.31 times as long as metatarsus; spinulae on ventral margin of tibiae and tarsi spine-like and strongly developed (lacking on metatibia). Chaetotaxy and porotaxy. Seta CO6 always distad; seta CO7 inserted proximally on procoxa and distally on meso- and metacoxa; position and number of secondary setae ( Table 1). Abdomen. LLAS ¼ 0.83–0.96 mm (mean ¼ 0.88 mm, n ¼ 3). Segment 8 subtrapezoidal dorsally, shorter than HW, LLAS/HW ¼ 0.68–0.82, truncate posteriorly. Siphon lacking. Urogomphus. Length of urogomphus ¼ 1.47–1.54 mm (mean ¼ 1.49 mm, n ¼ 3), 1.54–1.80 times as long as LLAS, 1.19–1.25 times as long as HW. Chaetotaxy and porotaxy. Urogomphus with several secondary setae.

3 rd Instar. As 2 nd instar except as follows. Color. Mottled pattern denser; urogomphus predominantly dark brown. Head. HL ¼ 1.93–2.02 mm (mean ¼ 1.98 mm, n ¼ 2); HW ¼ 1.69– 1.72 mm (mean ¼ 1.71 mm, n ¼ 2); FCL ¼ 0.81–0.83 mm (mean ¼ 0.82 mm, n ¼ 2). Cephalic capsule slightly longer than broad (HL/HW ¼ 1.13–1.17); apical margin of frontoclypeus with 40–45 spatulate lamellae clypeales; parietals with 11–12 lateral spines. Antenna. Length of antenna/ HW ¼ 0.66–0.70; A2. A1 » A3. A4, A2/A3 ¼ 1.23–1.31; A39/A4 ¼ 0.13–0.14. Maxilla. Galea 0.61–0.70 times length of MX 1; length of MX 3/ length of MX 2 ¼ 0.85–0.86.

Legs. Metathoracic legs about 1.20 times length of prothoracic legs, and about 3.30 times HW; femur. coxa. tibia » tarsus. trochanter (metathoracic leg); longest of metathoracic claws 0.30– 0.31 times as long as metatarsus. Chaetotaxy and porotaxy. Position and number of secondary setae ( Table 2). Abdomen. LLAS ¼ 1.20–1.39 mm (mean ¼ 1.29 mm; n ¼ 2); LLAS/HW ¼ 0.70–0.82. Urogomphus. Length of urogomphus ¼ 1.72–1.93 mm (mean ¼ 1.83 mm, n ¼ 2), 1.24–1.61 times as long as LLAS, 1.02–1.12 times as long as HW.

Source of Associated Material. The larvae of Allomatus nannup were collected in association with adults at the following locality: WEST AUSTRALIA, Mokerdillup Brook , 10 km. W. Bridgetown, 3480940E, 116839170S, 5.x.1999, S. Halse coll ; Blackwood river nr Bridgetown, 3385980E, 11680980S, 21.ix.2000, CHS Watts coll.

Figures

Figs. 1–2. Allomatus nannup Watts, Instar I. 1) Head capsule, dorsal aspect (color pattern not represented); 2) abdominal segment 8, dorsal aspect; AB ¼ abdominal segment 8, EB ¼ egg bursters, LC ¼ lamellae clypeales, FR ¼ frontoclypeus, PA ¼ parietale, and lowercase letters refer to primary setae and pores, respectively. Scale bar ¼ 0.10 mm.

Figs. 3–4. Allomatus nannup Watts, Instar I, metathoracic leg. 3) Coxa, trochanter, and femur, anterior surface; 4) coxa, trochanter, and femur, posterior surface; CO ¼ coxa, FE ¼ femur, TR ¼ trochanter, numbers and lowercase letters refer to primary setae and pores, respectively; non-identified setae and pores ¼ additional setae and pores (cf. material and methods). Scale bar ¼ 0.10 mm.

Figs. 5–6. Allomatus nannup Watts, Instar I, metathoracic leg. 5) Tibia and tarsus, anterior surface; 6) tibia and tarsus, posterior surface; TA ¼ tarsus, TI ¼ tibia, TR ¼ trochanter, numbers and lowercase letters refer to primary setae and pores, respectively; non-identified setae and pores ¼ additional setae and pores (cf. material and methods); pretarsus not represented. Scale bar ¼ 0.10 mm.