Medium-sized to large larvae, up to 11 mm long.
Antenna 5 segmented, consecutively shorter or segments 3 and 4 subequal in length. Ring organ on basal 1/4 of 1st segment. Blade slightly shorter or slightly longer than flagellum; accessory blade half length of blade. Lauterborn organs large. Style as long as combined length of segments 3 and 4.
Labrum with all S setae simple. Labral lamellae consisting of 4 narrow, pointed scales. Chaetae branched; spinulae simple, elongate. Pecten epipharyngis consisting of 3 simple scales, apically rounded. Ungula consisting of 3-4 pointed spines (perhaps=chaetulae basales) on distolateral corners; basal sclerite elongate, straight-sided, tapering to blunt apex. Premandible heavily sclerotised with simple to weakly bifid apex, and stout triangular inner tooth; brush absent
Mandible with apical tooth shorter than combined width of 4 inner teeth. Seta subdentalis short, pointed. Seta interna with long, unbranched basal part bearing 5 plumose branches. Inner margin with 1-5 long serrate spines, sometimes apparently absent.
Mentum with 1 broad median and 5 pairs of lateral teeth; lateral areas heavily sclerotised. Ventromental plates triangular, weakly sclerotised; beard absent. Setae submenti arising close to mentum.
Anterior parapods basally fused, each part with an apical crown of claws. Posterior parapods well developed, separate and each bearing an apical crown of claws. Procercus very short, bearing 2 long thick and 2-6 shorter, thinner anal setae, without subapical setae but 1 seta arising anterior to procercus. Supra-anal setae absent. Anal tubules shorter than posterior parapods. Anal end reduced with procerci lying dorsal to anal tubules. Body setae simple.
Cardiocladius is not clearly defined as different from Eukiefferiella, especially outside the Holarctic, where Afrotropical, Australian and Neotropical species challenge Holarctic-based diagnoses.
All larvae are associated with fast-flowing water, often associated with Simuliid larvae on which they may predate. Numbers may be very high below dam outflows, and on thin-water films of waterfalls, from temperate to tropics.