11-10-2024 TINTERN ABBEY, WEXFORD - SMALL TORTOISESHELL BUTTERFLY (Aglais urticae)

The small tortoiseshell (Aglais urticae) is a colourful Eurasian butterfly in the family Nymphalidae. Adults feed on nectar and may hibernate over winter; in warmer climates they may have two broods in a season. While the dorsal surface of the wings is vividly marked, the ventral surface is drab, providing camouflage. Eggs are laid on the common nettle, on which the larvae feed.

It is a medium-sized butterfly that is mainly reddish orange, with black and yellow markings on the forewings as well as a ring of blue spots around the edge of the wings. It has a wingspan ranging from 4.5 to 6.2 cm.

A bright foxy red ground-colour; the forewing with 3 black costal spots, whose interspaces are yellow, there being a larger black spot in the middle of the hindmarginal area and two smaller ones in the disc between the 3 radial and 2 median; hindwing with the basal half black; both wings with black submarginal band bearing blue spots. Underside of the forewing ochreous, with the costal spots as above, the apex and distal margin blackish; hindwing brown, basal half black with dentate edge, the whole surface with darker pencilling; at the distal margin of both wings contiguous dull blue lunules.

The small tortoiseshell is the national butterfly of Denmark.

It is found throughout temperate Europe, Asia Minor, Central Asia, Siberia, China, Nepal, Sikkim Himalayas in India, Mongolia, Korea and Japan, wherever common nettle, which their larvae feed on, is found. There are a few records from New York City which, however, are believed to be of introduced insects.

The small tortoiseshell butterfly tends to enter hibernation by mid to late September. Typically this butterfly will try to hibernate in dark sheltered locations. Because of this hibernation, they need to accumulate a lot of fat to survive the winter. The tortoiseshell needs at least 20% of its body weight in lipids in order to survive, making them much slower. Towards the end of their foraging for hibernation, they are much more susceptible to attacks by birds because of their low muscle to body mass ratio. During the first few weeks of hibernation, tortoiseshell butterflies are very susceptible to predator attacks. Up to 50% of the population hibernating in any given area can be eaten. The butterflies that hibernate in areas containing more light, and that are accessible to rodents who can climb, are the most susceptible to this type of predation. During hibernation tortoiseshell butterflies are able to supercool in order to keep from freezing. In sheltered areas, these butterflies can stand up to −21 degrees Celsius without freezing. However, they experience rapid weight loss during unusually mild winters.