The SCAN 01 Black Beetle from Devaux is one of my favourite models for selective trout fishing in reservoirs, lakes and all types of rivers.
It is effective from spring to autumn and has proven particularly effective on trout in Lake Drennec, among others.
Tied on a #12 barbless hook, the thorax is made of black/pearl Fritz chenille.
The elytra are made from two segments of EVA foam.
This model floats low but remains visible.
In low light conditions, it is a good idea to waterproof it with a floating liquid such as High N Dry, Tiemco Dry Dip Super or Dry Shake Liquid.
My personal choice as a professional guide specialising in fly fishing for trout in rivers and reservoirs.