Sperchon longissimus K.Viets, 1920

Records (Table 2): Benthos samples at one site in Gutland, 3 individuals (Gerecke et al. 2005), E1, 112 larvae, E4 9 larvae, E7 1 larva, parasitic on chironomids. Attribution by rearing larvae from females from spring no. Lux Qu19 (E1) and from a rheocrene in the north German lowlands (Dallbek­Quelle, Martin, unpublished data).

Description (n = 5, Lux Qu19 and Dallbek spring): Idiosoma moderately ovate; in non­engorged specimens, caudal idiosoma with a distinct but small indentation visible from both dorsal and ventral view (Figs. 21, 22). Length/width of idiosoma 215–255 (227)/155–205 (175).

Dorsal idiosoma (Fig. 21): Dp relatively long, but narrow (length/width 1.65). Anterior end of Dp straight, posteriorly sharpened, striated by relatively short lines. Length/width Dp 178–185 (181)/108–113 (110), Mp2­Amdp 42–47 (44), Mp1­Mp1 44– 48 (46), Mp2­Mp2 39–43 (41), Lp1­Lp 1 26–31 (29), Lp2­Lp2 69–73 (71), Mp1­Lp 1 9–11 (10), Mp2­Lp 2 22–25 (23), Mp1­Mp2 33–36 (34), Lp1­Lp 2 28–32 (30), Mp 1 30–32 (31), Mp 2 28–32 (30), Lp1 50–56 (52), Lp2 82–84 (83), Hu 79–82 (80), Mh1 79–86 (82), Mh2 75–84 (79), Mh3 67–72 (69), Mh4 52–61 (56), Lh1 72–79 (75), Lh2 66–73 (70), Lh3 54– 59 (55).

Ventral idiosoma (Fig. 22): Length/width CX­I 76–81 (78)/28–34 (32), CX­II 68–72 (70)/43–45 (44), CX­III 92–98 (95)/69–72 (70), coxal plates with a characteristic alveolar pattern; every honeycomb with an own sculpture (Fig. 22), urstigma rounded, C1­C2 40– 51 (44), C1­posterior margin of CX­I 20–26 (22), C1­Mmcp 17–21 (19), C4­Pmcp 71–80 (74), C1­C4 41–47 (45), C1 48–54 (51), C2 72–77 (74), C3 73–78 (75), C4 55–65 (60), length/width Expp 14–16 (15)/13–16 (14), E1­ E1 6 –7 (6), E2­ E 2 9 –12 (11), E 1 18 –20 (19), E 2 20 –24 (23), V1 45 –48 (47), V2 47 –53 (50), V3 53 –59 (56), V4 48 –56 (52).

Gnathosoma: Base 83–86 (84), length chelicera (Fig. 23) 71–75 (73), chela 12–20 (18), length/width P2 32–34 (33)/26–28 (27), length/width P 3 25–27 (26)/23–25 (24), two long setae of P5 with nearly the same length (Fig. 24), claw 14–17 (15).

Legs: All leg segments longitudinally striated, with the exceptions of the first segments (with a transverse lineation).

Leg I (Fig. 25): Total length 258–271 (264), length/height I­L1 (1se) 35–37 (36)/25– 25 (25), I­L2 (7se) 44–46 (45)/ 26–29 (27), I­L3 (4se, 1so) 51–53 (52)/24–26 (25), I­L4 (9se, 2so) 61–63 (62)/21–22 (22), I­L5 (13, 1so) 67–72 (69)/ 18–19 (19).

Leg II (Fig. 26): Total length 271–285 (277), length/height II­L1 (1se) 37–40 (39)/25– 26 (26), II­L2 (7se) 43–46 (44)/25–26 (26), II­L3 (4se, 1so) 53–55 (53)/23–25 (24), II­L4 (9se, 2so) 66–68 (67)/20–21 (20), II­L5 (13se, 1so) 72–76 (74)/15–19 (18).

Leg III (Fig. 27): Total length 352–368 (357), length/height III­L1 (1se) 61–63 (62)/ 23–25 (24), III­L2 (6se) 57–59 (58)/24–26 (25), III­L3 (4se, 1so) 68–72 (69)/20–21 (21), III­L4 (9se, 1so) 84–88 (85)/19–20 (19), III­L5 (12se) 82–86 (83)/14–15 (15).

Diagnostic characters of larvae: Characters of the dorsal plate (e.g. length/width>1.4, Lp2 <100 m).

Remarks: This is the first description of Sperchon longissimus larvae. The distinct indentation of the posterior idiosoma has also been found in S. squamosus (Ullrich 1976, see below) in which it is developed most obviously in unengorged specimens.