East-west splits in emergence

Yesterday I looked at differing emergence times at various latitudes. The alternative is to look at differences in eastern and western Britain.

Unfortunately I do not think there are quite enough data for northern England and Scotland, but there are plenty of data for 2015 for England and Wales south of the Humber-Mersey line. So I have split this area into four - firstly split at the 200 km level (approximately Thames-Severn) and then again at the 200 km mark - in essence using the junction between  ST and SU northwards to the junction between SJ and SK.

The results for 2014 and 2015 are presented below. They are not entirely convincing but I think it is possible to detect slightly earlier emergence in SW England. More analysis is needed!

Figure 1. Phenology of Eristalis pertinax in the east and west Midlands (west includes Wales) in 2015.

Figure 2. Phenology of Eristalis pertinax in south-east and south-wet England in 2015.