Cercyon analis (Paykull, 1798)

Rodriguez, Georgina & Archangelsky, Miguel, 2023, Larval chaetotaxy and morphometry of Megasternini: Cercyon (Paracercyon) Seidlitz, Cryptopleurum Mulsant and Pelosoma Mulsant (Coleoptera: Hydrophilidae), Zootaxa 5318 (1), pp. 45-66 : 48-50

Cercyon analis first-instar larva chaetotaxy

For general morphological characters of Cercyon larvae see B̂ving & Henriksen (1938); Quennedey (1965); Archangelsky (1997; 2016); Arriga-Varela et al. (2017).

Morphometry. Measurements and ratios in Table 1 .

Primary chaetotaxy. Head capsule ( Figs. 10–12 ). Frontale with 14 pairs of sensilla: two short setae on basal fourth, close to frontal lines (FR1); two pores (FR2) and two minute setae (FR3) close to midline at about midlength; two pairs of setae laterad to FR3 (FR5 short, FR6 long); one pair of pores posterior to inner margin of antennal sockets (FR4); one pair of pores (FR15) posterior to egg-bursters (EB); five pairs of sensilla distal to inner margin of antennal socket: two rather long setae (FR8, FR9), two pores (FR13, FR14) and one minute seta (FR10); slightly distal to this group one minute seta (FR12) and a pore (FR11); nasale with gFR1 bearing four dorsal short and stout setae, inner one on right side slightly longer, and a pair of short setae inserted ventrally, reaching anterior margin of nasale. Epistomal lobes lacking sensilla, therefore gFR2 absent; seta FR7 absent. Each parietale with 30 sensilla: dorsally with a basal longitudinal row of four minute setae (PA1, PA2, PA4, PA5); pore (PA3) not aligned with PA1, PA2, PA4, PA5, located closer to frontal line; one basal pore (PA6) almost touching frontal line; seta PA7 short, slightly distal to PA5; setae PA12, PA13 and PA14 closely aggregated on lateral margin at about midlength, two long and one short; seta PA8 long, near frontal line; pore PA10 anteromesal to group PA12-14; two setae (PA9 long, PA20 short) and one pore (PA19) in a transverse row on anterolateral corner of head capsule, PA19 closer to PA20 than to PA9. Ventral surface with three pores (PA23, PA24, PA25) and two setae (PA21 long, PA22 short) on anterolateral corner, close to mandibular acetabulum; lateral margin with one short lateral seta (PA11) on distal third and one pore (PA15) at about midlength; two setae (PA16 long, PA26 short) and one pore (PA17) closely aggregated at about midlength; one pore (PA27) and one long seta (PA28) at midlength closer to gular suture; one long seta (PA18) and two pores (PA29, PA30) on basal third, arranged in an oblique row, PA18 more distal and closer to lateral margin, PA29 more basal, closer to midline.

Antenna ( Fig. 13 ). A1 bare, with five pores, three dorsal (AN1 subbasal, AN2 and AN4 distal), and two ventral on distal margin (AN3 on outer surface, AN5 on inner surface). A2 with two pores, one distal (AN6) and one subbasal (■), and four setae, two subapical on outer margin (AN7 short, AN8 minute) close to base of SE1, and two subapical on inner margin (AN10 long, AN11 short). A3 with a group of at least four short sensoria on apex, one long and stout seta and one pore (gAN).

Mandibles ( Figs. 14–15 ). Both mandibles with six sensilla; one short seta on outer margin at basal third (MN1), one minute seta on outer margin at distal quarter (MN5) in right mandible (closer to apex in left mandible), three dorsal pores (MN2, MN3, MN4) forming an oblique row at level of inner retinaculum of right mandible (MN2 closer to MN4 than to MN3; equidistant on left mandible), MN3 closer to inner margin, more basal, MN4 on outer margin, more distal; pore MN6 subapical on inner margin.

Maxilla ( Figs. 16–18 ). Cardo with one short seta ( MX 1). Stipites asymmetrical, with a row of nine stout and short setae along inner margin, at least six bifid subapically; left stipes with basal four setae arranged in an oblique row, remaining setae forming a longitudinal row, basal seta of stipes likely homologous to MX 7, remaining setae forming (gMX2); right stipes with all setae arranged longitudinally. Ventral face of stipes with three pores, one on basal half ( MX 2), one subapical close to inner margin ( MX 3) and one subapical on outer margin ( MX 4), and two setae distal to pore MX 4 ( MX 5 shorter, MX 6 longer). MP1 dorsally with one basal spiniform seta ( MX 16) on inner face, MX 17 apparently absent; ventrally with two subapical setae MX 13 (long) and MX 14 (shorter) and two pores ( MX 12 on outer margin, MX 15 on inner margin at base of gAPP); inner appendage reduced, with four or five sensilla of different lengths (gAPP). MP2 with two pores, MX 18 ventral and apical on outer margin and MX 19 dorsal at inner margin on membrane connecting with MP3; one basal minute seta ( MX 27) on outer margin. MP3 with two rather long setae and two pores, one seta dorsal, close to outer margin ( MX 23), the other ventral on inner margin ( MX 21); both pores on ventral surface, one close to seta MX 21 ( MX 22), the other apical, close to outer margin ( MX 20). MP4 with one short basal seta dorsally ( MX 24) and two dorsal subapical pores ( MX 25 central, digitiform, MX 26 closer to outer margin); a group of at least seven or eight very short sensilla constitute gMX1.

Labium ( Figs. 11 , 19 ). Submentum with two pairs of setae ( Fig. 11 ), one short, basal (LA1), the other minute, on anterior margin (LA2). Mentum ventrally with one pair of short setae (LA3) and one pair of lateral pores (LA4), LA3 anteromesal to LA4, near the sclerite margin. Prementum with two pairs of setae (LA5 minute, LA6 long) and one pair pores (LA7) arranged in a transverse line, LA6 the innermost, LA7 located at the outer corner of the sclerite, LA5 inserted between LA6-7. Sensilla associated with ligula absent (LA9–12) except for one pair of pores (LA12?), placed on membranous lobe between labial palpi (behind palpi in ventral view). LP1 with one ventral seta (LA13, minute) and one distal pore (LA14, on inner margin of membrane); LP2 with one subapical pore on outer face (LA15) and a group of at least seven short sensilla that constitute gLA.

Figures

FIGURES 10–15. Cercyon analis, first instar larva. (10) head capsule, dorsal view; (11) head capsule, ventral view; (12) clypeolabrum, dorsal view; (13) antenna, dorsal view; (14) mandible, dorsal view; (15) mandible, dorsal view. Scale bars, Figs. 10–11: 0.05 mm; Figs. 12–15: 0.025 mm.

FIGURES 16–19. Cercyon analis, first instar larva. (16) left maxilla, dorsal view; (17) left maxilla, ventral view; (18) right stipes, dorsal view; (19) labium, ventral view. Scale bars: 0.025 mm.