(Meigen, 1818)
Body
Medium sized larvae up to 10 mm long. The anterior parapods are separate, the middle claws with 5 - 10 toothlets Cric(I) ornatus claws ant pp. The two posterior parapods bear rows of claws. Procercus is present. Two pairs of anal tubules present. On the abdominal segments 1 - 6 the L4 bundle consists of < 20 seta and is shorter than the segment Cric (I) sylv body seta. On segment 7, L4 consists of at least 3 setae (Hirvenoja, 1973; Moller Pillot, 1984b ).
Head
The head is yellow to brown with conspicuous dark cheeks (Moller Pillot, 1984b).
Antenna
The antenna has a normal length and consists of five segments. The small ringorgans on the antenna are both situated in the basal part of the first antennal segment Cric ornatus antenna.
Mentum
The mentum has one median tooth and 6 pairs of lateral teeth. Median tooth <2x the first lateral tooth. The second lateral tooth is reduced and partly fused with the first lateral# Cric sylvestris agg mentum
Labrum
The pecten epipharyngis consists of one compound scale Cric (Iso) pecten epiphary. SI is bifid. The premandible with 2 apical teeth Cric tibialis premandible (Hirvenoja, 1973).
Mandible
The mandible with a smooth inner side and the apical tooth is shorter than the joined inner teeth.
Differential characteristics
The setal tufts of L4 Cric (C) 14 Cric (I) sylv body seta on the abdominal segments are distinctive for Cricotopus (and Orthocladius holsatus). C. tremulus and C. lygropus have no setal tufts however.
C. ornatus can be separated from all other Isocladius (except. C. laetus) by:
the L4 bundle shorter than the segment, consisting of less than 20 seta
L4 on segment 7: 3 setae. C. ornatus can be separated from C. laetus by the claws of anterior parapods with 5 - 10 toothlets (C. laetus appr. 5); First antennal segment with round spots near the ring organ Cric ornatus antenna where in C. laetus one spot in the middle of the 1st segment Cric laetus antenna. The thoracic horn or C. ornatus is brown, while C. laetus has a transparent thoracic horn.