Two Woolly Jumpers

There is a thriving population of the small jumping spider Pseudeuophrys lanigera in my office building at University, which, with its species name meaning 'woolly' I think it deserves the common name of woolly jumper. I spotted one on the windowsill as I was going to close the blinds, and then another one descended from a thread of silk and ended up near the first one. Both were males and, after some swaggering and lifting of the front legs, one of them, the newcomer, retreated and followed on his way. It is the females that truly look 'woolly'. Males are very colourful, with dark and large front legs, red markings around the eyes and white moustaches and palps. These spiders are found on and inside buildings. They must consume minute prey, such as bark lice, springtails or small flies, although jumping spiders are able to tackle prey their own size. The adults can be found year round, although their peak season is June for females and September for males.

The smaller spider number 1, who held his ground.

The newcomer.

A Walnut orb weaver

It's not every day I find a new species of spider in the garden, so I was pleased this afternoon, when opening the garden gate I disturbed a young Walnut orb weaver, Nuctenea umbratica (above). It crawled up and hid in a crack between the planks of wood. This is a large and distinctive species, the females can reach 14 mm.
umbratica means 'of the shadows' in latin, which refers to their liking for dark cracks and crevices, where they hide during the day, aided by their wide and flattened abdomen. When discovered, they are often crouching in a characteristic position, which is the only explanation I can see to another common name: 'toad spider'. They can be very dark, almost all black, but this individual shows the wavy leaf-shape pattern on the abdomen, surrounded by a pale rim and pinkish sides with annulated legs. They like dry microhabitats, including wooden structures, like fence posts, dead wood, window frames (e.g. in birdwatching hides), greenhouses, and cliffs. They are mostly nocturnal, they emerge as it gets dark and make their stout, large orb web, of a similar shape to that of its relative Araneus diadematus, although they can also sit on their web during the day. Their tattered webs can be useful to detect the spider when found in suitable habitats during the day.
 Males peak in July and August, while females are found year round. I wonder if being a very large spider, like the garden spider Araneus diadematus, females may take two years to reach maturity.
Although I might have overlooked it due to its retiring habits, I keep finding it more often in recent years.

Adult N. umbratica in a window frame of a hide. (11/7/16, Tophill Low)

One of several N. umbratica adult female inside bird hide (11/10/15) Alkborough Flats.

A fresh egg sac found inside the same hide with several N. umbratica. It looks very similar in colour, shape and size to an Araneus diadematus egg sac.

An adult female N. umbratica sitting on her web during a dark November day inside a greenhouse (Thwaite Botanical Gardens, 3/11/15).

Sputnik spider and egg sacs

Yesterday evening, while pruning the plum tree, I found the distinctive egg sacs of the theridid Paidiscura pallens: they are white with pointy projections that make them look like the Sputnik satellite. The tiny mother, less than 2 mm in length, sat atop hers oversized egg sac, which was attached to the underside of the leaf and to the spiders loose, tangled mess of silk threads. She nervously moved back and forth from the sac and around it, like sensing that something was amiss. Despite finding the egg sacs regularly, this is the first time I see the female spider guarding it. I found another pair of egg sacs today under a plum leaf, also guarded by the mother.

Two Paidiscura pallens egg sacs also from today. 

The female and her two egg sacs from today.

Bees toiling for nectar

Many flowers, closely protect their nectar in deep nectaries (e.g. the Mint family) or behind barriers made by modified petals, like pea flowers. This way, unspecialised nectar feeders, which may not be good pollinators such as ants might not be able to access the nectar, but bees, which will visit many flowers in succession and are effective pollinators will be able to. These modified flowers have their pollen-bearing anthers on the roof of the modified petal blocking the entrance. The bee, while coming in to feed on the nectar, rubs its back on the pollen, ensuring she will pollinate the next flower she visits. Bees, however, often have to work really hard to get at the nectar.
 A few days ago I watched a common carder bee, Bombus pascuorum, feeding on Iris flowers (top photo). It tried to get in through the side unsuccessfully, but eventually found the way in pushing through the middle of the landing petal (which are called 'falls').
Later, a female Osmia caerulescens, landed on a Phlomis flower, she seemed to sense there was nectar behind the hooded petal closing the flower and pushed with her head until it managed to get under it. It spend quite a long time inside, I guess this is a nectar-rich plant and it will take a while to empty the nectaries for a small bee like this.

Osmia caerulescens getting in.

The bee just before leaving the flower after feeding.

Stretch spider portrait

I found this female stretch spider, Tetragnatha, in the garden this evening. I remembered that they have lovely faces and I gave it a try on the white bowl aiming for a frontal shot. They have their eyes in two rows, the bottom central pair facing forward. The face shot also allows to see its enormous fangs. After a short session in the bowl, I returned the spider to her leaf and she rapidly climbed to her retreat.

The resting position of Tetragnatha on a leaf.

Lekking long-horn moths

 In a walk by a wooded area on my way to work yesterday, I came across a few small swarms of dancing long-horn moths. I watched and waited until one of them sat to rest on the foliage: a Yellow-barred Long-horn moth, Nemophora degeerella. Long-horn moths are truly spectacular micromoths. Males are not only beautifully marked with metallic golden, chestnut and blue metallic stripes and a broad diagnostic yellow band across the wings, but their antennae are extremely long, several times their body length. It is astounding they can actually fly! Not only they can fly, but they perform a dancing flight, males bobbing up and down in a small area in shady wooded glades where they gather forming mating swarms or leks. These swarms, and possibly pheromones the males emit presumably serve to attract females and mate. Do females prefer males with longer antennae? These are day flying moths and I've watched the swarms in the morning or afternoon in warm sunny days in May and June. The antennae are white and so stand out as the moths fly. The antennae are strongly sexually dimorphic as the females, which I've never seen, are similar to males, but with short antennae. Their caterpillars feed on leaf litter.

 This is a short video of one of the moths appearing to sip honeydew from a leaf.

UPDATE 28/06/2017
A large swarm (over 20 moths) in the University Woodland area


via GIPHY

Why do male Wool-carder bees defend a flower patch?

I found the first male Wool Carder Bee, Anthidium manicatum of the year in the garden today, patrolling and basking on the large sage patch that is a favourite if many species of bee. If you have a flower-rich garden with a sunny aspect, chances are that in warm, sunny summer days you will see this chunky bee attacking other flower visitors, including large bumblebees. Male bees from most bee species often just hang around nests where they can mate as females emerge, or patrol flowers favoured by females. Occasionally they 'jump' onto or chase other bees or insects, possibly checking if they are females. For example, Male Hairy-footed flower bees, Anthophora plumipes, who emerge a week or so before females, will jump onto bluebottles, the only insect that roughly resemble the black females of his species. No other male bee is as aggressive actively defending a patch of flowers as Wool carder bees. They even have sharp spines at the end of their abdomen with they can use to harm, or even kill, other bees, so they rapidly become the only bees using the flowers

The abdominal spines of male Wool carder bees

 Most female bees mate once shortly after emergence, so males only had a chance of mating successfully early in the season. Females store the sperm of this early mating and use it to fertilise their eggs throughout the nesting season. Females will repel or avoid courting males vigorously once they've been mated. In contrast, Wool-carder bees are unusual in that females both mate multiple times and accept matings throughout their flight season. Witnessing solitary bees mating is quite rare, but with Wool carder bees, matings are quite frequent. Many females visiting a defended flower patch will mate with the resident male. The male defending a good flower patch will likely gain many matings with several visiting females, but, given what we know about sperm usage in solitary bees, will he benefit from fathering the female's offspring?

Mating Wool carder bees

 In a recent study, Kathrin Lampert and colleagues from Ruhr-University Bochum carried out some experiments to investigate why Wool Carder bee mating behaviour is so different from other bees. They in particular were interested in testing the hypothesis that Wool-carder bees might show what is known as 'late male sperm preference' in which the last male mating with a female has a disproportionally higher chance of fathering the females offspring.
 To find out 'who is the daddy' they used genetic testing in a similar way to how paternity is tested in humans, using genetic markers that have many variants, and therefore are likely to be different between individuals. In order to be able to capture the likely mothers and fathers of particular nests they constructed large flight cages containing Betony plants (for pollen and nectar) and Stachys byzantina (for plant wool, which the females collect to line their nest cells). Wool carder bees nest readily in sections of bamboo sticks, and they fixed artificial nesting sites inside the flight cages. Offspring of a female are found in a linear nest in consecutive order, the deeper cells in the bamboo stick contain the earlier laid eggs, while the cells closer to the entrance contain the later brood, which is likely to be male offspring. They carried out three experiments, in the first one, to test the feasibility of these experiments wild males and females (likely to have mated before) were captured, individually labelled with a dot of paint in the thorax, and released in the flight cage. In the second experiment, males in the cage were swapped to test if males with later access to females would father offspring. In the third experiment males were removed after a few days and females left to nest with no males, to investigate if females are able to store sperm. After the females had completed their nests in all the experiments, DNA samples were taken from the males and females, and them and the offspring found in the artificial nests screened for genetic paternity analyses.
A problem with their experiment were cleptoparasitic wasps, which destroyed the bee larvae and prevented genotyping. Another problem, which stems from bee's sex determination system, is that only female offspring have a dad: males develop from unfertilised eggs, so they only have a mum. They could only find out if offspring were male or female after genetic screening. Despite this, they obtained a number of female offspring from many females.
 The results revealed that the males flying with females at the time the females were provisioning a cell, where they are close to laying the egg, were the most likely fathers of the offspring (84% of the time), whereas most of the remaining fathers were males present in the cage in previous days, supporting the hypothesis of late male sperm preference. Males that were dominant, that is, chased away other males from flowers, tended to father more offspring, as most matings happened on flowers.
 The male removal experiment showed that females were able to store sperm for at least 11 days, and possibly much longer.
 This research suggests that a predisposition for late male sperm precedence in the ancestors of wool carder bees might have been what favoured the aggressive territorial behaviour seen in males, as they can benefit from monopolising floral resources visited by females.

More information
Lampert, K. P., Pasternak, V., Brand, P., Tollrian, R., Leese, F., & Eltz, T. (2014). ‘Late’male sperm precedence in polyandrous wool-carder bees and the evolution of male resource defence in Hymenoptera. Animal Behaviour, 90, 211-217.

Sharp-tail bees

It has been a while since I've seen a new bee in the garden. A couple of days ago it was sunny and warm and I watched the first male leaf-cutter bee Megachile willughbiella on a geranium. A while later a bee was basking on top of the fence post and I managed some distant shots. Its jaws looked very leaf-cutter like, but the end of the abdomen had some tell-tale spines, indicating it was a sharp-tailed bee Coelioxys sp. a bee I've only seen rarely in the local wildlife garden.
Although males and females sharp-tailed bees can be found nectaring at flower sources, they are cuckoo bees. The females do not collect pollen, instead, they are cleptoparasites, looking for ready made cells already provisioned with a pollen load. Their usual hosts are leaf-cutter bees, and their common name derives from their tapered abdomen of females, ending in a fine point, which is able to slice through the leaf wrappers of leaf-cutter bees, laying one egg either under the pollen load, or in between layers of the leaf wrapping of the cell before the cell is sealed. The cuckoo bee will also match the sex of her eggs to the host eggs sex, with the male eggs positioned in the outer cells of a nest. Once the larva hatches, they use their large mandibles to kill the host larvae or any other competitors. The cuckoos larvae complete their development and emerge at the same time as their hosts.
  I find the male abdominal spines very intriguing. What is their function? Coelioxys belong to the same family - Megachilidae - than Anthidium manicatum, the wool-carder bee, whose males are armed with formidable abdominal spines with a similar disposition. Male wool carder bees use these spines as weapons to defend their flower territory from other males and also other bees. They can fearlessly attack honeybees and large bumblebees, and are capable of killing them. It is unlikely that sharp-tailed bees use their spines in a similar way, as females do not collect pollen and there is no flower resources to defend. In the monograph Bees of the World, by Charles Michener, he hints at the spines being involved in dealing with the modified female's abdominal tip during copulation.
 There are eight species of sharp tailed bees in the UK, but in general they are very hard to identify without a specimen, so I will have to content myself with not having a definite identification for now.
 I have gone through my records of this genus in the wildlife garden, just five of them in June and July and here I show some record shots.

A male Coelioxys feeding on sage (12/6/10)

Female Coelioxys on birds-foot trefoil (4/6/2011).

Male Coelioxys resting. Many bees hold on with their mandibles in their sleep (10/7/2009).

Female Coelioxys on marjoram (2/7/2011).

Male Coelioxys on meadow cranesbill (11/7/2011).

Cuckoo bees tend to be rare bees, and sharp-tailed bees are no exception. The presence of cleptoparasites indicates a healthy host population. Often cleptoparasites decline and get locally extinct when a host population declines. In a study on sharp-tailed bees, about 3% of over 14,000 host cells (Megachile inermis) contained Coelioxys funeraria and less than 10% of Megachile relativa were parasitised. So, what about the hosts in my garden? The bee posts and bee hotels are commonly used by leaf-cutter bees of at least two species in my garden: Megachile willughbiella and Megachile centuncularis, used as hosts by several British Coelioxys species. Some species of Coelioxys are thought to parasitise Anthophora furcata, which is also a regular bee foraging and possibly nesting in the garden log piles. The synchrony of the hosts is remarkable as both male leaf-cutters and A. furcata, appeared in in garden in the last couple of days too.

This was the first of the year A. furcata in the garden, a male yesterday.

Male M. willughbiella, 29th May.

Male Megachile, possibly centuncularis, yesterday.

More information
Scott, V. L., Kelley, S. T., & Strickler, K. (2000). Reproductive biology of two Coelioxys cleptoparasites in relation to their Megachile hosts (Hymenoptera: Megachilidae). Annals of the Entomological Society of America, 93(4), 941-948.

Michener, Charles Duncan. The bees of the world. Vol. 1. JHU Press, 2000.

Falk, Steven and Richard Lewington 2015. Field guide to the Bees of Great Britain and Ireland. Bloomsbury, London. 432 pp.

Massive rainbow worm emergence

I woke up early this morning and went for a walk around the park. It was cold and it had rained a lot in the night. I had to watch my step as there were hundreds of blue-grey worms, Octolasion cyaneum, on the pavements and ground. This is a very colourful and common earthworm species, easily recognised by its yellow tail end and its orange clitellum (the central raised band) when adult. They are sluggish, live in topsoil and commonly emerge in large numbers after rain. Some individuals were the largest I've ever seen, over 26 cm! (bottom shot), although around 15 cm was much more common. I was surprised there weren't more blackbirds and thrushes feeding on this worm bonanza! Why do they come up in the rain? Reproduction can be ruled out as this species is parthenogenetic, that is, they can reproduce on their own, producing genetically identical offspring. Populations have little diversity and are made or clonal lines. Adult worms lay cocoons in the soil that contain singletons or twins.

More information
Lowe, Christopher N., and Kevin R. Butt. Life cycle traits of the parthenogenetic earthworm Octolasion cyaneum (Savigny, 1826). European Journal of Soil Biology 44.5 (2008): 541-544.

My conservatory spiders

The sun has been shining for a couple of days and it was warm enough that I started taking plants out of the conservatory into the garden and having a little tidying up. While doing this, I found a few spiders. Many were very tiny, very young individuals that I was unable to photograph properly and identify. Others were quite impressive. They have survived the winter in the dry, not too cold environment of the conservatory.
 First up, a Steatoda bipunctata, a false widow spider, which was on the side of a pot, a fully grown female. It has a very tick-like appearance, especially when it drops and tucks its legs in.

In between the bags of compost, I noticed the sheet webs of a Tegenaria. Here she is a bit camera shy, but shows her pretty abdominal patterns.

A few cob-webs came out of a corner, and then a Pholcus phalangioides ambled around trying to settle again.

This slim, fast and jumpy male Clubiona which I call black-face (possibly C. terrestris, but pedipalp examination is needed to confirm species) also featured on the top shot, fell from the foliage of a pot plant.

Finally, a Pardosa wolf spider on the window frame. There are dozens of young pardosa that have overwintered outside and sunbathe in loose groups on tiles and stones just outside the conservatory. This one got in through the crack of the window.

Winter active spiders in the house

We are having an exceptionally mild winter and, although much of the time it is wet and dull, winter invertebrates respond to the prevailing conditions. While some spiders overwinter in the safely of an egg sac, or as tiny spiderlings on leaf litter and tree trunks, others winter as grown young or adults. In warm conditions, some of these species overwintering as grown spiders continue to be active through the winter months, hunting or looking for mates. This post was prompted by a silky, silvery mouse spider Scotophaeus, that I found on the kitchen ceiling in the morning (above). So, I decided to investigate which other spiders were about inside and outside of the house. All the photos taken this morning.

Pholcus phalangioides.

The Pholcus spiders in my outside toilet, which is not heated, have been much more active than it is usual in winter. Pholcus adopts a curious flat position in cold conditions, but a large individual has been changing corners and looks gravid, or indeed very well fed.

Amaurobius similis with centipede prey

 In a crack at the bottom of the toilet door lives an Amaurobius similis. A couple of weeks ago I watched as a large springtail, Orchesella villosa, tripped one of her woolly silk lines. The spider sprung out like lightning out of her retreat, but the springtail, making use of its wonderful jumping abilities, escaped unharmed. Today the spider was luckier. I noticed she was out, which is unusual, and looking closer I saw she was busy with prey: a centipede, likely Cryptops hortensis.
What other spiders are out and about?
Inside the kitchen window, a mid-size garden orb-weaver Araneus diadematus, hung from her web. They occasionally wander inside and live on small plant midges or drosophila from the fruit bowl. Females have occasionally reached full size inside the house and attracted males.

A poor shot of an Araneus diadematus inside the house.

Zygiella x-notata legs visible touching its web.

On the sheltered top corners of windowsills you might find Zygiella x-notata, the missing sector spider, in a silky retreat, often next of her egg sacs and the empty wrapping, one of her front legs touching the guide thread to the center of her web. At night she comes out and sits in the middle of her web. They are active regardless the weather, building their new webs early in the morning even in hard frost.