Friday, 26 August 2016

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).

Sunday, 3 July 2016

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.

Wednesday, 29 June 2016

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.

Saturday, 25 June 2016

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.

Friday, 24 June 2016

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. Although I've never seen a female, they are similar to males, but with short antennae. The 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