Reiss, 1969
Body
Small to medium sized larvae up to 5 mm long. Segment 11 with a distinct hump Krenops fallax anal segments. The posterior parapods bear only simpel claws (Wiederholm, 1983).
Head
The S3 is simpel.
Antenna
The antenna stands on a tall smooth pedestal and consists of 5 segments. The basal segment is much longer than the flagellum. Segment 2 slightly expanded distally equal to or longer than the remaining segments, as long as or shorter than the third segment. The small Lauterborn organs on long pedestals that reach far beyond the apex Krenops fallax antenna.
Mentum
The mentum has a simpel median tooth and 5 pairs of lateral teeth Krenops fallax mentum. The ventromental plates are close together medially and wider than the mentum.
Labrum
SI is a comb and labral lamellae form a single plate with numerous apical teeth. The pecten epipharyngis consists of 3 smooth plates with distal teeth. The premandible has 2 teeth.
Mandible
The mandible with a dorsal tooth, apical tooth and 3 inner teeth all brown. The pecten mandibularis is present and seta interna with branches.
Differential characteristics
The dorsal hump on the 11 segment occurs in Krenopsectra Krenops fallax anal segments and Micropsectra fusca. Krenopsectra is only 5 mm long while M. fusca can reach a length of 10 mm. M. fusca is the only known Dutch Micropsectra without a distal spur on the antennal pedestal (Klink, 1982a).