３−３　Hydrobaenus　 group　（antenna with 6〜 7segments：ventromental plate transparent）　　　　　　　　　　　　　　　　　　　　　　　
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Hydrobaenus　　　Oliveridia　　 Parakiefferiella 　　　Heterotrissocladius 　　　　

Hydrobaenus

Body length 6〜7mm. graysh green. 2 species found in the country. They live in gentle flow, depth 1〜2m of sandy river bed.

（following pictuer :Hydrobaenus kondoi ）

Median teeth 1 pair. Lateral teeth with 6 pairs, the most outer tooth small. Ventromental plate crescent-shaped, not beard.	Ｓ�T:divided into 2, and even each diveded into 3〜4. Ｓ�U: thick,long needle like. Pecten epipharyngis 3 pointy lobes. Premandible bifid.	Antenna with 6 segments, basal segment long, antenna ratio 1.6〜2.0 :.6th segment very thin hair like, hard to see. segment 2 pale brown.
		・　Antenna with 6 segments, basal segment long, :.6th segment very thin hair like, hard to see. ・　medianteeth 1 pair, lateral teeth 6 pairs. 　　Ventromental plate crescent shaped, ・　Mandible : the size of apical tooth is length of 　2 inner teeth 　 　　seta subdentalis short, bifid. ・　Ｓ�T:divided into 2, and even each diveded into 　　3〜4 ・　Anal setae 7. ・　Anal tubules conical. ・　Claws of posterior parapod pale brown.

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Oliveridia

Large difference between Oliveridia and Hydrobaenus is form of mediantooth of mentum. Oliveridia with one mediantooth whereas Hydrobaenus with 2 teeth .
Body color various , grayish green 〜 bluish green .Body length ４〜６ｍｍ. Anal tubules long oval 〜 corn shape. Oliveridia distrivieted widely in the country, number of individuals is less. They live in clean water .

Mediantooth wide, pale brown. Lateral teeth 6 or 5 pairs, dark brown. Ventromental plate long oval, pale brown.		6th segment of antenna hair like.
		・Apicl tooth of mandible yellowish 　　　brown, 3 inner teeth dark brown. ・Ｓ�U: thick, long needle like. ・Labral lamella triangular. ・Premandible divided into 3. ・Pecten epipharyngis long lobes. 　choetulae laterals serrated. ・Anal setae 7.
Ｓ�T：bifid deeply , each with several teth .

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Parakiefferiella

Small larva , up to 4mm long. Body pale yellowish green 〜 pale bown . Eye spot 1 pair. They live in nomal or fast flow , in algae grown up the surface of pebble.
These larvae distributed widely in the country. About 10 species found .

Median tooth wide , pale yellow. Lateral teeth 5 〜 6pairs. Lateral teeth dark brown . Ventromental plate elongated.	Antenna with 6 segments,; 6th segment hair like. A strong style situated at apex of 2nd segment..
	・Mandible with 3 inner teeth. ・Ｓ�Twith variable number of branches . ・Ｓ�U: long needle like 　Pecten epipharyngis consistimg 3 subequal scales. 　Premandible spatula shale. ・Anal tubules 2 pairs , conical. ・Procercus about as high as wide. 6〜7 anal setae.

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Heterotrissocladius

Body length ５〜６ｍｍ . ,grayish green 〜 bluish purple. Head yellowish brown . Eye spot 1 pair.
Several species found in the country ; live in clear water, sandy pebble river bed.

		・Ｓ�T: plumose or palm shape. 　Ｓ�U: strong, long needle like.. ・Labral lamellae rounded , sclerotized ・Pectenepipharyngis consisting 3 scale-like. ・Premandible with 2 indistinct teeth. ・Anal tubules spidle or conical. 7 anal setae. ・Procercus higth longer than width。
2 Median teeth as wide as 3 lateral teeth. Lateral teeth 5 paits, Ventromental plate semicircular.
Antenna ratio 0.9〜1.２．; 7 segments. segment 3 short, segment 7 hair like. Blade not beyond tip of antenna .	Mandible : with 3 inner teeth. pecten subdentalis relatively long. Whole mandible dark brown.

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