Large, red to orange coloured, up to 15 mm long.
Frontal apotome without frontal pit, anteriorly separated from clypeus by straight suture; labrum present, lateral labral sclerites fragmentary.
Antenna with 6 segments. Lauterborn organs alternate on apices of segments 2 and 3, style apical on segment 3. Ring organ at base, or in basal third of segment 1, seta absent. Blade extending to near or beyond apex of antenna, accessory blade short.
SI coarsely plumose on each side; SII simple, or weakly plumose apically; SIII slender, relatively long; SIV normal. Seta premandibularis long and simple. Labral lamellae fused with modest number of blunt teeth. Pecten epipharyngis of three broad subequal untoothed scales, or with few large middle teeth and small lateral teeth (rydalensis group). Premandible with 3 or 5 teeth and strong brush.
Pale dorsal tooth present, moderately developed apical tooth and 3 inner teeth. Pecten mandibularis fine, sparse, not extending to apical mandibular tooth. Seta subdentalis inserted on ventral surface, simple, slender, long, straight or weakly curved and extending to innermost mandibular tooth. Seta interna inserted on dorsal surface, plumose, 4-5 branched.
Mentum with ventromental component of many teeth, the median trifid either pale or as dark as remaining teeth with very small median tooth (maybe absent), 5 lateral dorsomental teeth; dorsomental teeth on an even slope and evenly decreasing in size laterally. Ventromental plates separated medially by half width of ventromentum. Ventromental plate narrow, strongly curved; coarse striae relatively evenly spread across the plate. Setae submenti simple.
Lateral and ventral tubules absent.
Microtendipes belongs to a group of genera in which the larvae have 6 segmented antennae and alternate Lauterborn organs (excluding Lauterborniella and Zavreliella). The 3 usually pale median mental teeth and the 3 inner teeth of the mandible are characteristic, as is the clypeus which is separated from the frontal apotome by a straight suture. Omisus and Paratendipes larvae have 4 median mental teeth, 2 inner mandibular teeth and a frontoclypeal apotome. In Stictochironomus the first lateral tooth of the mentum is not lower than the second and the median mental teeth project beyond the lateral teeth. Paralauterborniella has a tall, pale, simple median tooth.
The description of the larva of M. rydalensis (Edwards) (Pinder 1976a) makes the introduction of 2 species groups possible. According to our present knowledge of the Holarctic fauna, M. britteni, M. chloris, M.diffinis and M. pedellus belong to the pedellus group, M. rydalensis and M. tarsalis to the rydalensis group. There are indications of further species groups in the Ethiopian region. The Palaearctic species caledonicus Edwards is placed in Omisus.
Species groups of Microtendipes
- 1. Median tooth of mentum pale or dark, appearing bifid, however, a third tooth is present, very much smaller than the other ones and depressed. Pecten epipharyngis with 3 equal sized teeth. Premandible with only 3 teeth ... pedellus group
- -- Median tooth of mentum always pale and distinctly trifid; teeth either of equal size or central tooth smaller. Pecten epipharyngis with several large middle teeth and a few small lateral teeth). Premandible with 5 teeth ... rydalensis group
Larvae of Microtendipes inhabit littoral and sublittoral sediments of larger bodies of still water; sporadically also in "Aufwuchs"; also in sediments and submerged mosses in running water.
About 17 species are known from the Holarctic. Thirteen species are known from the Afrotropical region, some of them doubtfully placed in this genus.