Medium-sized larvae, up to 10 mm long. Head uniform yellow-brown to brownish, antenna slightly darker; body greenish, spotted white. Head capsule elongate, entire surface with fine granulation; cephalic index 0.5. Dorsally, S5, DP and S7 almost aligned; S8 smaller and displaced posteriorly. Ventrally S9, S10 and SSm near aligned with long axis, VP position varying from anterior, directly lateral or slightly posterior of SSm. Setae simple, or bifid at most.
Almost 1/2 as long as head, 3x as long as mandible. Antennal ratio about 6.0. Basal segment about 13x as long as basal width, with ring organ at 0.45; segment 2 about 6x as long as wide; segment 3 2x as long as terminal segment. Style sclerotized in basal 1/2, extending beyond middle of segment 4. Peg sensilla very small. Blade extending beyond flagellum; basal ring about 1. 5x as high as wide. Accessory blade little shorter than blade.
Relatively slender, gradually tapered distally. Apical tooth 2.5x as long as basal width, 1/3 length of mandible; distal 1/2 blackish brown. Curved marginal lamella links proximally with blunt, oblique inner tooth; mola developed strongly as tooth with apically-directed point; seta subdentalis fine. Ventrolateral setae simple, situated adjacently on outer margin in basal 1/2 of mandible; seta 1 smaller than remainder, located very close to seta 2, seta 3 located roughly halfway between seta 2 and the proximal and somewhat ventral ring organ.
Basal segment of palp almost 4x as long as wide, with ring organ in middle.
Without fringe of swim-setae. Body integument longitudinally rugose. Anal tubules short, curved, horn-like, as long as wide, about 1/7 length of posterior parapods. Procercus 2.5x as long as wide, with 7 dark apical setae. Claws of posterior parapod variable; larger claws with fine spines on inner and/or outer margin; either 3 strong, medium-sized claws dark, 2 similarly-sized claws moderately darkened, or all pale; either one claw with weakly serrate inner margin, or 3 claws with serrate-dentate inner margins
Guttipelopia is easily distinguished from all other Tanypodinae by the granulose head capsule, rugose body integument and the broad pseudoradula.
Larvae of Guttipelopia live in shallow bodies of standing water, sphagnum bogs, ditches and the vegetated littoral of ponds and lakes, but may occur in streams in s.e. USA Coastal Plain: they may indicate eutrophic conditions. Two species are known from the Nearctic. Guttipelopia rosenbergi is rare and known only from Ontario and Manitoba, Canada. Guttipelopia guttipennis is Holarctic, extending from Canada to Florida, and in the Palaearctic eastward at least to the Angara River in Siberia.