Home > Moths > 14 June 2016 – Knot Grass

17 June 2016

14 June 2016 – Knot Grass

Knot Grass (Acronicta rumicis)

With the epic influx of Diamond Backs making BBC News, moths are now en vogue – bad news for cabbages, surprize news for moth enthusiasts. 

A trap put out on 13 June had plenty of lodgers, many of which were new to me: Silver Y, Fan-foot, Garden Pebble, Argyresthia trifasciata, Bright-line Brown Eye, Ingrailed Clay, Middle-barred Minor, Epiblema cynosbatella, Celypha lacunana, Scorched Wing, Shoulder-striped Wainscot, Small Angle Shades, and Water Carpet – but also the unrecorded Knot Grass. 

Knot Grass (illustration)

After staring at the ‘eyes’ on the forewing of this individual for a good while, I confirmed with Dr. Chesmore that my identification was correct – welcome to the Knot Grass (Acronicta rumicis). The first ever to be seen at Shandy Hall, it brings our species count to 373! This moth has a distinct chalky white mark near its trailing corner and a shaky white cross-line on the outer edge. ‘Akronux’ means ‘nightfall’ in Greek, probably a skew on Noctuidae, the name of its family, since this moth actually flies at night and not at dusk.

A illustration from 1843 (above) shows the Knot Grass next to a dewberry plant which belongs to the genus Rubus, after which the moth is named (rumicis). Another foodplant is the bramble and the moth used to be referred to as ‘bramble moth’, though this seems no longer to be in use. This moth has a stunning larval form with bright orange spiracles.

(Argyresthia trifasciata)

Like a shiny candy wrap, Argyresthia trifasciata is distinguished by the golden luster and three (tri-) stripes (fascia) on its wings. The only other time it has been recorded here was in 2013, since it is very local and quite scarce. I was very keen on getting all the micros identified (my co-worker remarked that I was turning into ‘the moth lady’), but was amazed at how many of them required dissection, which is where we draw the line.  Fortunately this moth is one that can be identified by observation only.

Post : Tung Chau (UPenn)