Cryptopleurum minutum (Fabricius, 1775)

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 : 53

Cryptopleurum minutum first-instar larva chaetotaxy

For general morphological characters of Cryptopleurum larvae see Archangelsky (1997).

Morphometry. Measurements and ratios in Table 1 .

Primary chaetotaxy. Head capsule ( Figs. 29–31 ). Frontale with 14 pairs of sensilla. Two short setae on basal quarter, close to frontal lines (FR1); two pores (FR2) and two minute setae (FR3) distal to FR1, close to midline; one pore (FR4) distal to FR3, near inner margin of antennal sockets; two pairs of short setae laterad to FR2 and FR3 (FR5 and FR6, FR5 slightly longer); one pair of pores (FR15) posterior to central area of nasale, behind egg bursters; five pairs of sensilla distal to mesal margin of antennal socket, three short setae (FR8, FR9, FR10) and two pores (FR13, FR14); one minute seta (FR12) and a pore (FR11) located anterodistal to the group form by FR8-10 and FR13-14; nasale with gFR1 bearing six setae, four dorsal short and stout and a pair of small setae inserted ventrally. Epistomal lobes strongly reduced, therefore gFR2 absent. Seta FR7 absent. Each parietale with 30 sensilla: dorsal surface with a basal longitudinal row of four minute setae (PA1, PA2, PA4, PA5) and one pore (PA3) located closer to frontal line; basal pore (PA6) almost touching frontal line; seta PA7 short, distal to PA5; setae PA12, PA13 and PA14 closely aggregated on lateral margin at about midlength, innermost one long, remaining two shorter; seta PA8 long, close to frontal line, behind antennal socket; seta PA9 short, lateral to antennal socket; pore PA10 lateral to seta PA8; pore PA19 and short seta PA20 on anterolateral corner of head capsule. 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 pore PA15 at about midlength and two short setae, PA11 (distal to pore PA15) and PA18 on basal third; a transverse row of two pores (PA27 and PA17) and two setae (PA26 very short, PA16 long) at distal third, PA27 closer to base of submentum; rather long seta PA28 behind pore PA27; basal fourth with two pores, PA29 closer to midline and slightly posterior to PA30.

Antenna ( Fig. 32 ). A1 bare, with five pores, three dorsal (AN1 on basal third, AN2 subapical, AN3 subapical on outer margin), remaining pores ventral and subapical, (AN4 and AN5). A2 with two dorsal pores, distal one (AN6) and subbasal one additional (■), and four setae on membrane connecting with A3, two on inner margin (AN10 rather long and AN11 very short), two on outer margin (AN8 and AN7 very short). A3 with a group of at least four or five sensilla (gAN).

Mandibles ( Figs. 33–34 ). Both mandibles with six primary sensilla: one rather long seta on outer margin at basal third (MN1), one minute seta on outer margin at distal third (MN5) in right mandible (closer to apex in left mandible), three dorsal pores (MN2, MN3, MN4) forming an oblique row at about midlength, MN3 closer to inner margin, more basal, MN4 on outer margin, more distal; pore MN6 present, subapical on inner margin.

Maxilla ( Figs. 35–36 ). Cardo with one short seta ( MX 1). Stipes dorsally with a row of seven short setae along inner margin (basal five setae stouter and bifid apically); basal seta of that row likely homologous to MX 7, remaining setae forming (gMX2); ventral face with three pores, one on basal half ( MX 2), one at distal fourth close to inner margin ( MX 3) and one on outer margin ( MX 4), two long setae distal to pore MX 4 ( MX 5, MX 6). MP1 dorsally with one basal spiniform seta ( MX 16), pore MX 17 apparently absent; ventrally with two subapical setae ( MX 13 long, MX 14 short) and two pores ( MX 12 on outer margin, MX 15 on inner margin at base of gAPP); inner appendage reduced, with several sensilla of different lengths (gAPP). MP2 with two apical pores, one ventral near outer margin ( MX 18) and one dorsal near inner margin ( MX 19); one basal minute seta ( MX 27) on outer margin. MP3 with two rather short setae and two pores, one seta dorsal ( MX 23), on outer margin, the other ( MX 21) ventral on inner margin; both pores ( MX 20-22) on ventral surface, one ( MX 22) close to seta MX 21, the other ( MX 20) on outer margin. MP4 with one short basal seta dorsally ( MX 24) and two dorsal pores, one ( MX 25) digitiform and central, the other ( MX 26) close to outer surface; a group of seven or eight very short sensilla constitute gMX.

Labium ( Fig. 37 ). Submentum with two pairs of setae ( Fig. 30 ), basal one (LA1) rather short, the other (LA2) minute, on anterior margin. Mentum ventrally with one pair of short setae (LA3) and one pair of lateral pores (LA4). Prementum ventrally with one pair of setae (LA6 short) and one pair of lateral pores (LA7), dorsally pores LA8 absent; sensilla associated with ligula absent (LA9–11) except for one pair of pores (LA12?, covered by base of palpi therefore not illustrated for first instar larvae; see Fig. 47 of third instar larvae); seta LA5 apparently absent in first instar larvae. LP1 ventrally with one minute seta (LA13, ventral) and one distal pore (LA14, on membrane connecting with LP2); LP2 with one subapical pore on outer face (LA15) and a group of six or seven short sensilla that constitute gLA.

Figures

FIGURES 29–34. Cryptopleurum minutum, first instar larva. (29) head capsule, dorsal view; (30) head capsule, ventral view; (31) clypeolabrum, dorsal view; (32) antenna, dorsal view; (33) mandible, dorsal view; (34) mandible, dorsal view. Scale bars, Figs. 29–30: 0.05 mm; Figs. 31–34: 0.025 mm.

FIGURES 35–37. Cryptopleurum minutum, first instar larva. (35) left maxilla, dorsal view; (36) left maxilla, ventral view; (37) labium, ventral view. Scale bars: 0.025 mm.

FIGURES 44–47. Cryptopleurum minutum, third instar larva. (44) right maxilla, ventral view; (45) right maxilla, dorsal view; (46) left stipes, dorsal view; (47) labium, ventral view. Scale bars: 0.025 mm.