Isoperla grammatica - Yellow Sally
The Yellow Sally is a medium-sized stonefly and very common on Welsh
rivers and streams; its slow, creeping nymph spends most of the time
beneath stones where trout are unable to find it. When ready to transpose
to a winged adult, the nymph moves into the shallows. Usually it leaves
the water either by crawling up emergent vegetation or by climbing onto a
partly submerged stone.
The adult appears as a sulphur yellow blur in the summer
sunshine, and it is one of the very few insects that 'hatch' during the
heat of the day. A related species, the Large Yellow Sally (Chloroperla
torrentium) is very similar apart from size and is also most likely to
be seen during the daytime.
Top of page... |
