Gilfach (west) has become the latest and fourth 1 km square in the valley to reach the 100 species mark following on from Blaencaearu (117), Garnwen (west) (111) and Lletty Brongu woods (102).
Within the square there are multiple habitats including pine forestry, clear-fell, country lanes with large numbers of umbellifers in season, farm fields and mountain moorland. This enables a wide variety of hoverflies to be recorded many of which are either firsts for Wales and Glamorgan or rarities. The elevation is on average 250 metres above sea level but is the first mountain near the coastal region so is a natural gateway to the valley for migrants also.
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Recording begins in week 12 (march) where spring hoverflies mass on the over abundance of Sallow blossom. Numbers continue to build to a crescendo at week 26 (late June) when 35 species can be seen in a day. There is a bit of a lull of 2 weeks before the second broods and late summer hoverflies emerge and peak at week 33 (mid-August) with the possibility of 40 species in a day. After that numbers tail off and recording stops at week 37 abruptly because all the flowers have faded and there is no Ivy in the square and hoverflies are easier to find elsewhere in the valley.
Seasonal highlights
Spring - Cheilosia caerulescens, Cheilosia chrysocoma, Ferdinandea cuprea, Sericomyia lappona, Criorhina ranunculi.
Summer - Criorhina ascilica, Xylota tarda, Xanthogramma stackelbergi, Psilota anthracina, Eupeodes lapponicus.
Autumn - Eriozona syrphoides, Eristalis rupium, Rhingia rostrata, Scaeva pyrastri, Scaeva selenitica
hoverflies in red are rare or scarce for Glamorgan or Wales and those in blue are migrants.
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