Saturday, 16 April 2016

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.

Monday, 14 March 2016

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.

Wednesday, 27 January 2016

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.

Sunday, 15 November 2015

Wandering male lace weavers

In the last week I have found two different males Amaurobius similis wandering, one in the porch and the other in the house. Note the different abdominal pattern in the photos below, especially the dark blotches surrounding the cardiac mark (the midline elongated area over the abdomen). In this species, mature males are most likely to be found between September and November, and they abandon their webs in search of the female retreats. I released them both after taking their photo paying especial attention to the palp (above), which is diagnostic and separates this species from the similar one A. fenestralis. Males A. similis have an inward pointing, curved sharp projection on its palp, which in A. fenestralis is thicker and blunt.
Male 10/11/15.
Male 15/11/15.

Tuesday, 3 November 2015

Spiders in glasshouses

Today at work, I had the chance of inspecting some glasshouses in the Thwaite Botanical Gardens of the University of Hull. They are heated glasshouses holding cacti, succulents, ferns and other plants from around the world. I was pleasingly surprised by the diversity of spiders in them. I found a single Woodlouse Spider, Dysdera crocata, under a bin (above). Quite fitting as we were collecting woodlouse for a practical on woodlouse diversity. The students were quite impressed!
 The first surprise was to find several Walnut Orb Weavers, Nuctenea umbratica. We dislodged an individual from a tree growing in a pot and it proceeded to play dead, legs drawn in, as they do when disturbed. They are usually nocturnal, spending the day in a crack in bark, but this large female I found later was sitting in the middle of her web, I wonder if the reason is it was a very dark, overcast day. There were many more smaller sized individuals, also sitting out in their webs, and it is quite likely this spider matures on her second year of age.
Mature female Nuctenea umbratica.
A student pointed this female Tegenaria to me, she found under a tarpaulin.
A mature, gravid Araneus diadematus sitting on her web.
This was the second nice surprise. One of the glasshouses held a healthy population of Garden Centre spiders, Uloborus plumipes.
By the toilets, a number of Pholcus phalangioides.
Where there are windows, there are window-frame spiders, Zygiella x-notata
I found a single Ero sp. egg sac. These spiders abandon their characteristic egg sacs, and they are not the easiest to find.
On a window ledged, a female Araneus diadematus looking like it has seen better days. Its abdomen shrivelled. Her days are counted after she lays her eggs and weaves her egg sac.