Description of the preimaginal stages of Enochrus (Hugoscottia) variegatus (Steinheil, 1869) and E. (Methydrus) vulgaris (Steinheil, 1869) (Coleoptera: Hydrophilidae), with emphasis on larval morphometry and chaetotaxy Author Byttebier, Barbara Author Torres, Patricia L. M. text Zootaxa 2009 2139 1 22 journal article 10.5281/zenodo.188528 7baefce2-2948-418b-8850-d74f24cbbfff 1175-5326 188528 Enochrus ( Methydrus ) vulgaris (Steinheil, 1869) ( Figs. 2 , 7–10 , 18–21 , 24–25 , 28–29 , 31 ) Material examined. ARGENTINA : Buenos Aires City: “Golf Club Lagos de Palermo”, 3 breeding adults collected on 02.xi.2006 by B. Byttebier. Buenos Aires City: Ecological Reserve “Costanera Sur”; 6 breeding adults collected on 02.xi.2006 by B. Byttebier ( 10 egg cases, 17 instar I, 5 instar II and 7 instar III larvae, 3 pupae , 5 emerged adults). Diagnosis. Larvae . Coronal sulcus short (instar I) or very short (instar III); left mandible with one inner tooth; AN10 and AN11 subapically on the second antennomere; stipes with MX 4–6 distally on outer margin, located on a longitudinal row; PA26 closer to PA27 than to PA17; sterna III–VII with a pair of prolegs, each one bearing a group of cuticular spine strongly curved as hooks. Egg case ( Fig. 2 ). Total length = 4.34–6.75 mm, width = 1.91–2.36 mm; length without mast = 2.48–3.47; mast length = 1.86–4.09 mm. Eggs, laid out without specific order pattern inside the egg case. (length = 0.52–0.67 mm, width = 0.27–0.35 mm). Number of eggs variable in each egg case, between 14 and 17 (N = 6). First-instar larva ( Figs. 7–10 , 18 ). Morphometric measures detailed in Table 2 . Color . Head capsule dark brown. Antenna, mandible and labium light brown. Maxilla light brown with maxillary palpomere darker in some specimens. Thoracic tergites dark brown, thoracic appendages light brown; membranous areas of the thorax grayish brown. Abdominal sclerites, urogomphi and lateral appendages of abdominal segment VIII dark brown; membranous areas of the abdomen grayish brown. Head capsule ( Figs. 7–10 ). Coronal sulcus short. Mandible . Left mandible with one inner tooth. Thorax . Prosternum composed by one undivided plate with a basal notch. Abdomen . Sterna III–VII with a pair of prolegs, each proleg bearing a group of cuticular spine strongly curved as hooks ( Fig. 31 ). FIGURES 26–29. Enochrus variegatus , legs of first-instar larva: 26, prothoracic leg, anterior view; 27, prothoracic leg, posterior view. Enochrus vulgaris , legs of third-instar larva: 28, metathoracic leg, anterior view; 29, metathoracic leg, posterior view. Scale bars = 0.05 mm. FIGURES 30–31. Enochrus variegatus , prolegs of third-instar larva: 30, proleg bearing a group of cuticular spines. Enochrus vulgaris , prolegs of third-instar larva: 31, proleg bearing a group of hooks. Scale bar = 0.05 mm. FIGURES 32–34. Enochrus variegatus , first-instar larva: 32, habitus, dorsal view. Enochrus variegatus , pupa: 33, dorsal view; 34, ventral view. Scale bars: Fig. 32 = 0.02 mm, Figs. 33–34 = 0.5 mm. Chaetotaxy ( Figs. 7–10 , 18 ). Head capsule ( Figs. 7–10 ). Ventral surface ( Fig. 10 ) of each parietale, with sensilla PA26–PA28 located on a longitudinal row, very close to each other (PA26 closer to PA27 than to PA17). Antenna ( Fig. 18 ). AN10 and AN11 situated subapically on outer margin of second antennomere. Maxilla . Stipes with MX 4–6 located distally on outer margin, on a longitudinal row. Labium. LA2 located on the membranous area between submentum and mentum ( Fig. 10 ); LA6 very long (1/3 longer than in E. variegatus ). Legs . Ligula without apical processes. Chaetotaxy of legs summarized in Table 3 . Second-instar larva . Similar to first-instar larva except for the following features. Morphometric measures detailed in Table 2 . Chaetotaxy . Head capsule. Parietale with 10–12 secondary sensilla: 3 setae and 1 pore close to PA8–PA9; 4–5 setae on the lateral margin; a row of 2–3 setae between PA6 and PA7. Mandible. With 5–7 secondary sensilla. Labium . Ligula without minute process apically ( Fig. 24 ). Legs . Chaetotaxy summarized in Table 3 . Third-instar larva ( Figs. 19–21 , 24–25 , 28–29 , 31 ) Similar to second-instar larva except for the following features. Morphometric measures detailed in Table 2 . Head capsule ( Fig. 21 ). Coronal sulcus short or very short, in general difficult to distinguish. Thorax . Prosternum composed by one subdivided plate with an incomplete sagittal line on more than the basal third. Chaetotaxy ( Figs. 19–21 , 24–25 , 28–29 ). Head capsule. Each parietale with 9–11 secondary sensilla: 3 setae and 1 pore close to PA8–PA9; 4–5 setae on the lateral margin; a row of 1–3 setae between PA6 and PA7. Mandible ( Figs. 19–20 ). With 7–8 secondary sensilla. Labium ( Figs. 24–25 ). Each lateral margin of mentum with 4 stout secondary setae. Legs ( Figs. 28–29 ). Chaetotaxy summarized in Table 3 . Pupa . Body . TL (excluding pronotal styli and cerci) = 3.25–4.40 mm; MW = 1.14–1.59 mm. Head . Maxillary palpi extending to first abdominal segment. Abdomen . Segment I with 2 pairs of styli situated on a transversal row.