The Common Blue can be seen over most of the grassy areas around the site, but is most prolific on the meander area. The total number of individuals seen over the five years is the greatest for any species, and its numbers have held up well over the period. This presumably indicates that the amount of its caterpillar foodplant, bird’s foot trefoil, has not declined due to the increasing rabbit activity in the meander area. There are two broods separated by a gap in June or July, but, although every year has this gap, the timing is sufficiently variable that the mean profile is continuous.

The Holly Blue is generally seen flying fairly high at tree level rather than low over grass as the Common Blue does. Consequently it is most commonly seen near the more wooded areas of the site. It has two distinct broods, the first in April and May, when the females lay on holly bushes, and the second in July and August, when they lay on ivy. There is plenty of ivy around the site, but I have not specifically looked for the occurrence of holly bushes. The very large variation in numbers seen, from 1 in 1995, to 33 in 1997, and back to 2 in 1999, is related to the well-known 6 or 7-year cycle that it undergoes, thought to be due to interaction with the host-specific parasitic wasp Listrodomus nycthemerus. The variations closely mirror the abundance over the whole Upper Thames area (and probably nationally), as shown graphically in the leaflet for the Millennium project issued by UTB in April 1999.