A drop of nectar
Small tortoiseshell on a flower in the gardens of Muckross House south of the town of Killarney, County Kerry, Ireland
Some background information:
The small tortoiseshell (Aglais urticae) is a colourful Eurasian butterfly that belongs to the family Nymphalidae. It is found throughout temperate Europe, Asia Minor, Central Asia, Siberia, China, Nepal, India, Mongolia, Korea and Japan, wherever common nettle is found, which their larvae feed on. The small tortoiseshell is the national butterfly of Denmark. 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.
Adults feed on nectar and may hibernate over winter. In warmer climates these butterflies 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. As with several nymphalid butterflies, the caterpillars feed on stinging nettles (Urtica dioica) and small nettles (Urtica urens). However, common hop has also been recorded as larval food plants.
Adults overwinter in hibernation, emerging on the first warm sunny days of the year to mate and breed. In southern parts of the range there may be two broods each year, but northern insects are inhibited by the long length of summer days from breeding a second time. Small tortoiseshell butterflies usually begin to emerge from their pupa from mid-June into August. They tend to enter hibernation by mid to late September. Typically these butterflies will try to hibernate in dark sheltered locations.
Because of this hibernation, they need to accumulate a lot of fat to survive the winter. Small tortoiseshell need at least 20% of their 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.
In 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 become the prey of birds. During their 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.
After hibernation, nectar is one of their main sources of nutrients. The compound eyes of small tortoiseshell butterflies enable them, to differentiate between various flowers through visual signals. They tend to prefer colours at both ends of the visible light spectrum for humans. These correspond to the colours violet and red respectively.
The wings of tortoiseshell butterflies help conceal them extremely well from predators. When closed, their wings look like leaves, helping them to hide. On the ground, it may take birds up to 30 minutes to see them. In addition to this, when discovered, tortoiseshell butterflies will flick their wings open to reveal bright colours. While they don't have eyespots like many other butterflies, these bright contrasting colours can often scare a predator, giving the tortoiseshell butterfly ample time to escape. These butterflies are also particularly fast. When discovered and attacked by birds, they usually fly away in straight lines in order to outstrip the predators.
Small tortoiseshells were once among the most common butterflies in Europe and temperate Asia. But nowadays, these butterflies are in very rapid decline, at least in Western Europe. This decline cannot be explained by the decline of their host plant, because the nettle is still widespread. However, small tortoiseshells are severely affected by summer droughts. During periods of drought, the butterfly experiences a vastly reduced reproductive rate. Another crucial factor is the timing of rainfall. If there is not adequate rainfall in the early summer, the food plants are not able to fully develop, leaving the larvae without a suitable source of nutrition. Hence, declining rainfalls and increasing summer droughts might be a reason for the decline of this butterfly species.
A drop of nectar
Small tortoiseshell on a flower in the gardens of Muckross House south of the town of Killarney, County Kerry, Ireland
Some background information:
The small tortoiseshell (Aglais urticae) is a colourful Eurasian butterfly that belongs to the family Nymphalidae. It is found throughout temperate Europe, Asia Minor, Central Asia, Siberia, China, Nepal, India, Mongolia, Korea and Japan, wherever common nettle is found, which their larvae feed on. The small tortoiseshell is the national butterfly of Denmark. 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.
Adults feed on nectar and may hibernate over winter. In warmer climates these butterflies 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. As with several nymphalid butterflies, the caterpillars feed on stinging nettles (Urtica dioica) and small nettles (Urtica urens). However, common hop has also been recorded as larval food plants.
Adults overwinter in hibernation, emerging on the first warm sunny days of the year to mate and breed. In southern parts of the range there may be two broods each year, but northern insects are inhibited by the long length of summer days from breeding a second time. Small tortoiseshell butterflies usually begin to emerge from their pupa from mid-June into August. They tend to enter hibernation by mid to late September. Typically these butterflies will try to hibernate in dark sheltered locations.
Because of this hibernation, they need to accumulate a lot of fat to survive the winter. Small tortoiseshell need at least 20% of their 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.
In 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 become the prey of birds. During their 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.
After hibernation, nectar is one of their main sources of nutrients. The compound eyes of small tortoiseshell butterflies enable them, to differentiate between various flowers through visual signals. They tend to prefer colours at both ends of the visible light spectrum for humans. These correspond to the colours violet and red respectively.
The wings of tortoiseshell butterflies help conceal them extremely well from predators. When closed, their wings look like leaves, helping them to hide. On the ground, it may take birds up to 30 minutes to see them. In addition to this, when discovered, tortoiseshell butterflies will flick their wings open to reveal bright colours. While they don't have eyespots like many other butterflies, these bright contrasting colours can often scare a predator, giving the tortoiseshell butterfly ample time to escape. These butterflies are also particularly fast. When discovered and attacked by birds, they usually fly away in straight lines in order to outstrip the predators.
Small tortoiseshells were once among the most common butterflies in Europe and temperate Asia. But nowadays, these butterflies are in very rapid decline, at least in Western Europe. This decline cannot be explained by the decline of their host plant, because the nettle is still widespread. However, small tortoiseshells are severely affected by summer droughts. During periods of drought, the butterfly experiences a vastly reduced reproductive rate. Another crucial factor is the timing of rainfall. If there is not adequate rainfall in the early summer, the food plants are not able to fully develop, leaving the larvae without a suitable source of nutrition. Hence, declining rainfalls and increasing summer droughts might be a reason for the decline of this butterfly species.