Species Account

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Distribution

Summary Data

Season (Adult / Immature):

National Status: Migrant

Local Status: Scarce and local migrant/wanderer.

Local Record: Grade 3 See here for explanation

Flight time: Arrive Apr-Nov.

Forewing: 12-14mm.

Foodplant: Knotgrass.

IMPORTANT - Please note that the maps and accounts are provisional, subject to change and further update. The whole dataset still needs to go through the final verification process and it is likely that a very small number of records will not satisfy the present requirements and there are other records that have not been formally submitted. The information is for guidance only.

Record breakdown:

	VC9	VC11	Region
Year first recorded	1905	1983	1905
Year last recorded	2011	2011	2011
Number of records	920	49	1938
Number of individuals	1761	59	3640
Unique positions	128	9	274
Unique locations	105	9	228
Adult records	907	49	1912
Immature records	0	0	0

For the region, we have a total of 1938 records from 228 sites. Earliest record on file is in 1905.

Photos

Species Account

For further information refer UK Moths.

Davey, P., 2009: A strongly migratory species headquartered south of 40°N that ranges from a near annual in southern England, to a relative rarity in northern Scotland. The species does not appear to be able to survive the UK winter in any stage. The adult, has an unmistakable uniform lemon-yellow ground colour with a single diagonal pink stripe, and assumes a roof-like, tectiform posture when at rest. In Dorset, the moth has been recorded in twenty-four of the past twenty-seven years. In favourable seasons, immigrants spawn resident broods when the larvae feed on knotgrass (Polygonum aviculare) and equal-leaved knotgrass (Polygonum rurivagum). Colonies are occasionally found in stubble fields where knotgrass grows. One such colony with an estimated two hundred freshly emerged and emerging moths was found in a derelict weedy potato field covered in knotgrass near Durlston lighthouse on 11 September 1947. "The range of colour forms in this colony was remarkable with no two examples alike, and several pink ab. sanguinaria were noted. A similar emerging colony was discovered at Langton Herring during the same week" (A Russell). Since 1947, instances of regularly trapped 'home-grown' pink or semi-pink Vestals have occurred in 1983, 1989 and 1992. In each of these years, primary immigrant yellow Vestals were trapped during the May to July period.

The inability to survive the UK winter is demonstrated by the contrast in the phenomenal season of 2006 and the utter dearth in numbers in 2007. The linear distribution of records across the county during immigration, suggest that Vestals fly at altitude on migration, a characteristic shared with a few migrant micromoths such as Plutella xylostella⁴⁶⁴, Nomophila noctuella¹³⁹⁸ and Palpita vitrealis¹⁴⁰⁸. For many other immigrant species, observations tend to increase exponentially towards the coast in any given immigration event, and for these, low altitude flight is likely to be the norm. The phenology of this species likely reflects the multiple brood-cycle of resident colonies in Iberia and north-west Africa; increasing numbers spawned by the northward colonisation of mainland Europe as the season progresses, result in a quadrupling on average of sequential brood peaks up to mid-September.

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