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Biology: Larvae hatch in July/August and enter fresh thin
shoots. The "boatsman" hibernates twice as larva in rhizomes
of common reed. In May/June larvae mine in several young shoots.
To change shoots, larvae cut a 2-3 cm long portion of an internode
(picture 54) and use it as protection to swim to another shoot (picture
39). During summer one year old larvae move into the rhizome, where
they will hibernate. Two year old larvae pupate between May and
July usually in an internode below water. Adults emerge between
June and July below water and lay eggs on shoots or leaves.
Description: Larvae up to 35 mm
long, head light brown, larval body yellow to olive-green (picture
34), covered with microscopic stupples; pupa embedded in a silky
tube leading to the emergence window (picture 53), pupa case very
thin; fore wings of females beige colored, fore wings of males brown
with dark spots (picture 41).
Feeding pattern/damage: Feeding
by larvae of Schoenobius gigantellus in spring cause characteristic
damage to reed shoots. At least one internode is intensively eaten
out, but there is always a thin layer of the epidermis intact (picture
55). Shoots completely die off afterwards. In addition, larvae cut
shoots completely to change to another shoot. Infested internodes
are repeatedly subdivided by silky layers. Hibernating larvae cause
nearly no damage to rhizomes.
Distribution: Europe, Asia
References: Goater,
1986; Häfliger et
al., 2001
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Pic. 54: Shoot cut by Schoenobius gigantellus
Pic. 55: Feeding of Schoenobius gigantellus
Pic. 39: Larva of Schoenobius
gigantellus moving to new shoot
Pic. 34: Larva of Schoenobius gigantellus
Pic. 53: Pupal chamber of Schoenobius gigantellus
Pic. 41: Male of Schoenobius gigantellus
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