Warming up painted lady

Cloudy, with intermittent showers today. A cold Painted Lady sat 'shivering' on a bush in the garden and allowed me a close approach. The shivering appearance was due to the butterfly revving its flight muscles, what I had never seen before. I have to apologize - to the butterfly - that I had to use flash, as it was dark and I wanted to emphasize the effect of its wings movement. A few moments later, the butterfly flew away.

A view of the Painted Lady's wing underside.

On this frontal shot the first modified pair of legs are visible just under the butterfly's eyes. 

Emergence of Winged ants

For a couple of weeks now, sunny spells after showers bring out a nervous anticipation in ant colonies. The workers come out en masse and run frantically around the colony entrance holes, often in cracks on street pavements. I have stopped a couple of times to watch this but so far no sign of winged queens and males. Yesterday though, we got the first glimpse of emergence of winged ants (Black Garden Ant, Lasius niger). Emergence happens during July and August and sometimes is very synchronic around the country. Workers seem to keep them in, while they stand high on their front legs, as if sniffing the air with their antennae, appearing to check that everything will be fine for their reproductive brothers and sisters. They have to sort out predators - sparrows and many other insect eating birds love them - during their mating flight. Queens will mate and then find a suitable hole where to dig their first colony. They might live for over a decade, sheltered in their nest taken care of by their daughters. Males will die shortly after mating.

Home-grown Painted Ladies

All of a sudden, Buddleia blooms across the city today were decorated with fresh-looking bright coloured Painted Ladies (Vanessa cardui). The contrast with the faded, worn first individual I photographed this year (see this previous post and also an extreme example here) was stark. Most of today's butterflies were likely to have been born in the U.K., the offspring of the migrating individuals. It is unclear how many generations of Painted Lady happen every year, as there is a lot of overlapping. According research carried out by the Spanish researcher Constanti Stefanescu, the whole cycle outdoors takes 6 to 8 weeks depending of the temperature, and he estimated 3 to 4 generations for NW Spain. The number of generations must be more limited here, with the cooler climate, and is likely that these fresh-looking butterflies will become the returning generation and they are not interested in breeding anymore, but in fattening up for their lengthly return to North Africa

Feeding against the sky

A fresh Painted Lady sunbathing on a wall

More information
Stefanescu, C. (1997) Migration patterns and feeding resources of the Painted Lady butterfly, Cynthia cardui (L.) (Lepidoptera, Nymphalidae) in the northeast of the Iberian peninsula. Miscel.lania Zoologica, 20: 31-48.

What are slugs up to on your kitchen floor?

Late last night I went to the kitchen and found a couple of large yellow slugs entwined on the kitchen floor. I dashed back to the front of the house to grab the camera but in the few seconds that took me do do it - it is a well rehearsed sprint of mine - they had started going their separate ways. The sudden flash of light when switching on the kitchen light must have shocked them and they went shy. The only indication they had been together was a circle of slime on the tiles. Should I carry my camera with me as I walk around the house? I sometimes think so. I knew nothing about the yellow slug mating habits. The yellow slug Limax flavus is not as good-looking as its relative the Leopard Slug, Limax maximus of fame due to its acrobatic sex featured in David Attenborough's Life in the Undergrowth TV series (see also the fantastic photos in Snail's Tails). I found very little, well, yes, as snails they are hermaphroditic and exhange sperm, although self-fertilisation is not unheard of. I also found a clip of the start of courtship, which happens on the ground. So I am afraid I will have to wait and see if I can catch them again. I cannot believe I am going to look forward to see slugs at home.

The sunspot owners: Speckled Wood butterflies

Male Speckled Wood perched on his sunny spot

The Speckled Wood (Pararge aegeria) butterfly is largely a new millennium butterfly in East Yorkshire. Probably due to the warming climate in the British Isles, the range of this butterfly is gradually increasing north. I saw the first Speckled Wood in Hull in a disused cemetery with large trees and lush undergrowth in 2005. This is a woodland and hedgerow species, not often found feeding on flowers. Adults feed mainly on tree canopies on honeydew, a lovely name for the sugar-laden aphid and scale insect sticky secretions. The most obvious individuals are males, which defend sunlight spots on the woodland floor. They rest on exposed, sunny leaves and inspect any butterfly or insect that passes by. Other butterfly species are briefly checked before the males come back to their resting place, females are courted, and intruding Speckled Wood males that come down from the tree canopy are chased in a brief spiral flight. This territorial behaviour was investigated in a classic paper by Nick Davies in woodland near Oxford. He visited the woodland daily and carried out lots of simple experiments with Speckled Wood individuals marked with colour spots. This way he was able to describe in detail the movements of each individual butterfly. Individual males spent all day in a sunny spot in the woodland floor, fluttering around and perching in it, and following faithfully the sunny spot as it moved though the day on the woodland floor. One of the most interesting findings of this study is that every time an intruder entered a sunny spot, and was involved in a 'spiral flight' with the owner, the intruded ended up retreating to the tree canopy and the resident took its position in the sunny spot. In all the spiral flights observed, over 200, the resident always won regardless of his condition. Davies concluded that the spiral flight is not a 'fight' but a courteous exchange of pleasantries: "to put it anthropomorphically, the owner says 'I was first here and the intruder says 'Sorry, I didn't know there was anybody occupying the sunspot, I'll retreat back to the canopy'. The reason the intruder comes down into the canopy is that it doesn't know the spot is taken. Davies carried out some experiments in which he introduced a male into an already occupied sunspot without the resident male noticing (he remarks he failed frequently, as the resident male seems to be always on the lookout for intruders). In the five occasions he succeeded, the spiral flight escalated and was more lengthy than usual, as both males regarded themselves as the territory owners. Only a few seconds of residency were enough for them to consider themselves the spot owners. Males were competing for the sunny spots and the tree canopy males readily occupied empty spots. The reason for this competition is that females often visit these sunny spots and therefore, males defending a sunspot are more likely to mate. The males on the canopy do not defend a territory but patrol the trees up and down in search of the rarer females. 

Female Speckled Wood

Male perched on his sunny spot