A rare species in Belgium, but probably overlooked due to it resemblance with B. lunaris.

The larva lives under dead bark of various trees (but especially on Ulex) and other shrubs. It hibernates. Pupation in the larval feeding place.

The adults fly from early June till early September. They come to light.

ID; very similar in appearance with B. lunaris, but B. lambdella differs in being larger, coloration more ochreous-yellow, costal suffusion narrower, thorax and tegulae concolorous with forewing, base of black lambda broader with costa  rounded.