Hampshire and Isle of Wight Butterfly and Moth Society
Hampshire and Isle of Wight Butterfly and Moth Society
| Family: | Lycaenidae |
| Subfamily: | Polyommatinae |
| Genus: | Lampides |
| Species: | boeticus |
| Authority: | (Linnaeus, 1767) |
The Long-tailed Blue is an extremely rare migrant to the British Isles. It was first recorded from Brighton in East Sussex, and Christchurch in Hampshire, in August 1859. By 1939 a mere 36 sightings had been recorded - mostly of individuals. Between 1940 and 1988 another 85 sightings were recorded. The only major immigration was in 1945, a good year for migrants in general, when there were 38 sightings. A recent immigrant was observed in Hampshire in 2006.
However, the most noticeable influx occurred in 2013 when Long-tailed Blue were seen at 9 sites in Devon, Hampshire, Sussex, Kent and Suffolk. Mating pairs, eggs and larvae were also found, confirming that the species had successfully bred and, on 8th September 2013, the first of the offspring emerged in Wiltshire and Kent. Sightings from other counties followed, with sightings continuing into October.
On the continent, this butterfly is considered a pest of pea crops, one of the larval foodplants, where it can cause considerable damage. This butterfly is continuously-brooded on the continent but is unable to survive our winters. Although this species is a rare migrant to the British Isles, it is one of the most-widely distributed Lycaenids in the world. The vast majority of records in the British Isles are from the south of England and the Channel Islands.
| #Individuals | #Tetrads | 2023 | 2024 | Abundance Trend | 2023 | 2024 | Distribution Trend |
|---|---|---|---|---|---|
| 40 | 6 | -85% | 5 | 2 | -60% |
| #Records | #Individuals | Earliest Record | Latest Record | |
|---|---|---|---|---|
| All Records | 54 | 85 | 10/03/2018 | 13/11/2022 |
| 2024 | 5 | 6 | 18/9/2024 | 24/10/2024 |
| Location | Date | Quantity | |
|---|---|---|---|
| Earliest Record | Boscombe | 18/9/2024 | 1 |
| Latest Record | Mount Joy | 24/10/2024 | 1 |
| Highest Count | Southbourne | 20/9/2024 | 2 |
One of the issues with 'raw' trend data is that there is inherent bias based on the number of recorders. For example, the number of individuals and populated tetrads recorded are likely to increase if there is an increase in the number of recorders. In order to remove this bias, the normalised trends use data that has been recalculated using the average number of recorders over the trend period. This normalisation gives a much better picture of the true trends.
Average #Recorders: 1.64
Average #Recorders: 1.64