Limbodessus masonensis
Creators: name: Michat, Mariano C.
name: Alarie, Yves
name: Watts, Chris H. S.
Publisher: name: Zenodo
Year: 2012
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Dytiscidae
Limbodessus
Limbodessus masonensis

description: <i>Limbodessus masonensis</i> (Watts &amp; Humphreys, 2001) (Figs 111–114) <b>Source of material.</b> Two specimens of instar II and two of instar III were used for the description (Table 1). Larvae were collected in association with adults at the following locality: Australia, <b>Raeside palaeovalley</b>, Lake Mason calcrete, Salt Well, BES 14361, 27.586S, 119.5218E, 20–IX–2006, coll. W. F. Humphreys and T. Moulds. <b>Diagnosis (instar III).</b> Medium-sized species (HL 0.55–1.15 mm); head (Fig. 111) subpentagonal; nasale subtriangular; half-circle of dense spinulae on lateroventral margins of nasale absent; hole-like structure on ventrodistal surface of nasale absent; lateral margins of nasale not inflated in dorsal view; lateral branches of nasale well developed; slender spinulae anterior to seta FR13 scarce (20 or less); occipital foramen well developed (HW/ OCW less than 1.90); occipital suture present; lateral margins of parietal straight; secondary spiniform setae on lateral margins of parietal scarce; seta AN2 present; distal half of MN broad; setae LA3, LA4, LA5 and LA8 hairlike; secondary setae on U absent (Fig. 114). <b>Instar I.</b> Not available. <b>Instar II.</b> Head. A3 less than 2.50 times longer than A1; A4 less than 0.70 times as long as A3; MN less than 4.70 times longer than broad; MP2 1.05–1.45 times longer than MP1; MP2 2.10–2.95 times longer than MP3; LP2 1.00–1.70 times longer than LP1. Legs. L3 2.25–2.95 times longer than HW; CL(L3) less than 0.40 times as long as TA. Abdomen. U 3.00–4.00 times longer than LAS; U more than 2.25 times longer than HW; U1 less than 1.45 times longer than U2. Chaetotaxy. Anteroventral margin of nasale with 25 lamellae clypeales distributed in a single row; anterior secondary setae on proCO absent; meso- and metaCO with less than 5 posterodorsal secondary setae; ventral secondary setae on pro- and mesoCO present; proFE with less than 3 posteroventral secondary setae; metaFE with less than 11 secondary setae; anterodorsal, anteroventral and posterodorsal secondary setae on proTI absent; anterodorsal secondary setae on meso- and metaTI present; secondary setae on proTA absent; posterodorsal secondary setae on meso- and metaTA present; posteroventral secondary setae on meso- and metaTA absent; metaTA with less than 4 secondary setae; secondary setae on U absent. Measurements and ratios that characterize the body shape are shown in Table 5. Secondary leg setation detailed in Table 13. <b>Instar III</b> (Figs 111–114). Head (Fig. 111). A3 less than 2.25 times longer than A1; A3 less than 1.45 times longer than A2; MN less than 4.85 times longer than broad; MP less than 1.75 times longer than labial palpus; MP2 2.10–3.10 times longer than MP3; LP2 more than 0.65 times as long as LP1. Legs (Figs 112–113). L3 2.25–2.85 times longer than HW. Abdomen (Fig. 114). U 2.40–3.10 times longer than LAS; U 1.55–2.25 times longer than HW; U1 0.70–1.40 times as long as U2. Chaetotaxy. Anteroventral margin of nasale with 50 lamellae clypeales distributed in 2 rows; pro- and mesoCO without anterior secondary setae; pro-, meso- and metaCO without posterior secondary setae; proCO with less than 11 secondary setae; metaCO with less than 20 secondary setae; anterodorsal secondary setae on pro- and metaFE present; metaFE with less than 12 anteroventral secondary setae; posterodorsal secondary setae on meso- and metaFE absent; metaFE with 9–27 secondary setae; anterodorsal secondary setae on proTI present; anteroventral and posterodorsal secondary setae on proTI absent; mesoTI with less than 4 anteroventral secondary setae; metaTI with less than 9 anteroventral secondary setae; metaTI with less than 16 secondary setae; secondary setae on proTA absent; anterodorsal and posteroventral secondary setae on meso- and metaTA absent; anteroventral and posterodorsal secondary setae on meso- and metaTA present; mesoTA with less than 7 secondary setae; metaTA with less than 16 secondary setae; secondary setae on U absent. Measurements and ratios that characterize the body shape are shown in Table 10. Secondary leg setation detailed in Table 18. <b>Remarks.</b> This species belongs to the group characterized by the absence of secondary setae on the urogomphus (<i>L. challaensis</i>, <i>L. exilis</i>, <i>L. fridaywellensis</i>, <i>L. hillviewensis</i>, <i>L. hinkleri</i>, <i>L. leysi</i>, <i>L. millbilliensis</i>, <i>L. morgani</i>, <i>L. ordinarius</i>, <i>L. pulpa</i>, <i>L. raeae</i>, <i>L. windarraensis</i>, <i>L. yuinmeryensis</i>) (Fig. 114). Larvae of <i>L. masonensis</i> can be distinguished from any other species of that group by the following combination of features: lateral margins of the nasale not inflated in dorsal view (Fig. 111), mandibles less than 4.80 times longer than broad, shorter legs, presence of anterodorsal secondary setae on the protibia (Fig. 112), absence of anteroventral secondary setae on the protibia (Fig. 112), absence of secondary setae on the protarsus (Figs 112–113), presence of anteroventral secondary setae on the mesotarsus, and absence of posteroventral secondary setae on the tarsus (Fig. 113).
description: Published as part of <i>Michat, Mariano C., Alarie, Yves &amp; Watts, Chris H. S., 2012, 3584, pp. 1-110 in Zootaxa 3584 (1)</i> on pages 56-59, DOI: 10.11646/zootaxa.3584.1.1