The Blues are a subfamily of the “Gossamer-winged” butterflies, the Lycaenidae. The two other subfamilies are the Coppers and the Hairstreaks. The adults are small, generally under 5 cm across, and often quite brightly coloured. With many species, the larvae tend to be flat, emit scents and sounds that attract ants, which then often take care of the larvae, feeding them until they pupate.

The Blues in Hadlow consist primarily of the Holly Blue, the Common Blue and the Brown Argus. The Holly Blue is a very light, almost silvery, blue butterfly that is commonly found at waist height or above in Hadlow gardens searching for one of its two food plants, holly in the spring, ivy in the autumn. Its larvae are very unusual in using different food plants at different times of year, and also not involving ants.

The Common Blue male is a good clear blue on the upperside of its wings of grassy meadows and footpaths that is generally found in the countryside of the parish, although it may wander into built up areas occasionally. The male’s underwings are a neatly spotted light brown. The female however is not blue at all and is a subtly patterned spotted brown on both its upper and lower wings. It can be quite easily confused with the Brown Argus.

The Brown Argus is the third “Blue”, but it has a slightly different pattern of spots on brown on both its males and females. It is classed as a blue for good taxonomic reasons, although this might seem a bit strange initially. It is not an easily found butterfly in the parish, but a few can be found in several different areas and in most years.