Rivulet or Small Rivulet?

Rivulet or Small Rivulet?

Observation - Rivulet or Small Rivulet? - UK and Ireland. Description: Wingspan 20mm, forewing 13mm. Apart from size the difference between the Rivulet and Small Rivulet appears to be the presence of a single indentation at the midpoint on the front of the cross bar on the Rivulet vs. a double notch for the Small Rivulet. T

Wingspan 20mm, forewing 13mm. Apart from size the difference between the Rivulet and Small Rivulet appears to be the presence of a single indentation at the midpoint on the front of the cross bar on the Rivulet vs. a double notch for the Small Rivulet. This specimen appears to have a single notch - but still I'm not 100% sure. Attracted to MV Skinner trap.