Medium sized larvae, up to 6 mm long. Head brownish; body white. Head capsule oval; cephalic index 0.60. Dorsally S5 slightly posterior to S8, S7 clearly anterolateral to S8, DP smaller than the dorsal setal sockets; S7-S8-DP-S5 almost aligned. Ventrally, S9-S10-VP-SSm forming gentle curve; VP bigger than setal sockets. S5 trifid, other setae simple.
Not quite 1/2 as long as head, rather more than 2X as long as mandible. Antennal ratio 0.3-0.4. Basal segment about 8X as long as basal width, with ring organ between 05 and 0.7; segment 2 about 7X as long as wide; segment 3 as long as terminal segment. Style clubbed apically, extending to middle of terminal segment. Peg sensilla large, as long as segment 3, seated opposite and fused with the margin of the segment into a tuning-fork-like appearance. Blade extending to terminal segment; basal ring about 1.5X as high as wide. Accessory blade as long as flagellum.
Strongly curved, gradually tapering towards apex. Apical tooth 2.5X as long as basal width, 1/4 length of mandible. Inner tooth, elongate, apically-directed, extending to seta subdentalis; accessory tooth pointed swelling at base of apical tooth; mola developed distally as very large tooth, as long as width of apical tooth, with rounded, apically-directed tip; seta subdentalis large. Ventrolateral setae situated in distal 1/3 of basal 1/2 of mandible, more or less equally-spaced on outer margin; pit of seta 1 somewhat smaller than that of other setae; ring organ located somewhat proximal to seta 3.
Basal segment of palp 3X as long as wide, with ring organ at 0.7.
Without fringe of swim-setae. Anal tubules spindle-shaped, 3.5X as long as wide. Procercus 3X as long as wide, with 7 apical setae. Claws of posterior parapod simple, all yellowish; larger claws with fine points on inner and/or outer side.
Living larvae of Krenopelopia are conspicuous by their white colour. Amongst the group of Pentaneurini with 'tuning-fork' shaped peg sensilla and a large mandibular molar expansion, Krenopelopia can be differentiated by the presence of a dorsal pit and the points of the inner ligula teeth being curved outward. The medially-recessed ligula is shared only by some Monopelopia and Pentaneurella, and the bifid paraligula distinguishes from Denopelopia. The transversely aligned SSm, VP, S9, S10 is unique to Krenopelopia in this grouping.
Larvae of Krenopelopia are cold-stenothermic. In central Europe they are characteristic inhabitants of springs, in northern Europe they colonize the littoral of cold lakes. They occur in muddy seepage areas, even remote from flowing water: in central European springs larvae favour the terrestrial/aquatic boundary zone.
The genus is essentially Holarctic in distribution with two species described from the Nearctic: K. narda from Alaska, and perhaps Oregon (Roback, 1983) and K. hudsoni, known from eastern North America from Ohio (Bolton, 2007) and s.e. USA (Epler 2001, Hudson et al., 1990). Seven species are known from the Palaearctic, 2 from the western Palaearctic (K. nigropunctata and K. binotata) and 5 from Japan after synonymy (Kobayashi and Endo, 2008). Otherwise Krenopelopia is known only from Singapore (P.S. Cranston pers. obs.) and Indonesia.