Orange-tip

The Orange-tip (Arthocharis cardamines) is one of the first butterflies to appear in the spring. Here, in Manorhamilton (Ireland), they're on the wing from April until early June. The male, being territorial, can be seen incessantly fluttering about in search of female and warding off other males. I have even seen them chasing off members of other species, in particular, Small white (Pieris rapae) and Green-veined White (Pieris napi britannica), which, like the Orange tip, are members of the Pieridae family.
The bright orange wing tips, which gives the butterfly its name, probably serves as a display to attract females and as a deterrent to other males.
The female, in contrast, keeps a low profile. Her wing tips are black, instead of orange, and can only be seen flying when feeding or searching for plants to lay her eggs on.

Male Orange-tip. The tips of the female are black. ©Sara Garcia Hipolito 

Both male and female are very flighty and hard to approach, as the slightest movement will set them off. The best time to get close to them is when the weather is not good enough for them to be active. At this time they can be found resting on plants, with a preference for those with light colour flowers. When at rest, the butterfly will keep its wings closed, so only the white and green under-wing is visible. This helps them blend with the environment, while their asymmetrical green pattern helps to break their silhouette, giving the butterfly pretty good camouflage against predators.  

When at rest, only the white and green under-wings are visible. ©Sara Garcia Hipolito

 The two most common plants where you can find their eggs are Ladies' Smock (Cardamine pratensis) and Garlic Mustard (Alliaria petiolata). I have observed a strong preference for Ladie's Smock, except for one site were there was a higher proportion of eggs on Garlic mustard. Several eggs can be seen in a single plant at different stages of maturation. I have often wondered whether they're all laid by the same female or by different. A recent sighting of a female who, after actively searching through a patch of flowers for over five minutes, went off without laying any eggs, leads me to think that they possibly avoid laying their eggs in plants where eggs from other females are already present. This would make sense, as the caterpillars are said to be cannibalistic, so the eggs of any butterfly that are laid in a plant that already has eggs would be doomed, as the caterpillars from the first eggs would hatch sooner and eat the late arrivals.
Despite much searching, I still haven't been able to find any caterpillars, even when I have returned to look in plants where I had found eggs.

Eggs at different stages of development. The orange egg is at a more advanced stage than the yellow ones and will eventually tun brown. ©Sara Garcia Hipolito

Above: Map of local sites where my observations were made. Below: From the chart, it can be seen that the Orange-tip is the 4th most abundant butterfly in the area. Map and Charts by the Irish National Biodiversity Data Centre, using data by Sara Garcia Hipolito.

For more information on the Orange tip butterfly, please visit the Irish Biodiversity Data Centre's page on this species:
 http://records.biodiversityireland.ie/species_in_focus/index.php?sifk=AnthocharisCardamines