Sunday, 26 January 2014

Porcellio scaber - Common Rough Woodlouse

Found this little chappie wondering around the floor of the downstairs toilet the other day. A little bit of detective work on the web and using the few books insect reference books that detail woodlice, I was able to make a tentative identification and name him a common rough woodlouse. That is not demeaning him in anyway, but that's his common name. He also goes by the much more impressive name of Porcellio scaber.


Common rough woodlice are considered native to mainland Europe, but has spread throughout the world, including onto isolated islands such as Hawaii and Marion Island (located between Africa and Antarctica) and is found on every continent, excluding Antarctica. This spread has probably been aided by export of plant material.

Part their success could be due to the wide range of habitats they live in. They live under leaf litter, rocks, and fallen logs in forests, meadows, and gardens, and are frequently found in splash zones, dunes and salt marshes.

The allusion to the body surface in the common name can clearly be seen in the photographs. It has a warty body surface with two short tails (uropodia) on their final body segments (nelsons).

Woodlice lack a waxy cuticle on their exoskeleton, leaving them more at risk of desiccation (drying out due to excess water loss) than other members of the arthropoda such as insects and spiders. As a result of this, much of their behaviour is concerned with avoiding desiccation, seeking damp areas out of light.



They have seven body segements, each with a pair of legs, and their bodies are divided into three sections: head, pereion (thorax), and pleon (abdomen), and their heads are divided into three lobes. 

Their two pleopodia (appendages under their pleons), have pseudotrachia, allowing for respiration through their pseudolungs. These pseudolungs appear as white patches on the abdomen, and they are unable to be closed to prevent water loss. 



One thing that did surprise me was how long the life span of P. Scaber can be. It has been suggested that this species typically lives 2-3 years, though up to 90% die within a month of emerging from their brooding pouches.

References:

Reggio, C. Porcellion Scaber. Animal Diversity Web. http://animaldiversity.ummz.umich.edu/accounts/Porcellio_scaber/

Friday, 10 January 2014

House Spider Panic

Last night there was much consternation and gnashing of teeth from the front room as my daughter settled down to watch Celebrity Big Brother as a large spider crawled up the wall in front of her. I springing immediately into action, but only after I had taken a few photos, but the pressure was definitely on to "get it out of here!".


It is one of three or four possible Tenegaria species, though there are 11 species that occur in the UK and Northern Europe (1). All of which are very similar and can only be identified to species by genitalia. With no microscope of any idea of what I should be looking all I can do for now is get it to genus, confirmed via iSpot. However, judging by the palps it is a female. The most likely species it could are:

Tegeneria domestica (Common House Spider), body size up to 10mm. This is perhaps the most common but smallest of there species. Although virtually reliant on people's houses, this species can be found in cave entrances and inside hollow trees (2). They spin a sheet web that leads to a tubular retreat, in a corner if a room or behind a piece of furniture. Strands of silk extend beyond the main platform of the web forming a tangle of lines. Females hang their dirty-white egg sacs from ledges using a few strands of silk.


Tegeneria gigantea, in some sources it is named T. duellica (Cobweb Spider), body size up to 18mm. Tegenaria saeva and T. gigantea are identical in size and appearance and can only be separated by the form of the male palp and of the female epigyne in mature individuals (2). However, there does seem to a difference in distribution between the two with T. duellica tends to have a more easterly distribution (2). Based upon the distribution map shown below it is less likely that our lady is T. duellica, though it is possible.


Tegeneria saeva, body size up to 18mm. The distribution of both T. saeva (red) and duellica (green) are shown on the right (2). The brown area shows the overlapping distribution.

Tegeneria parietina (Cardinal Spider), body size up to 20mm. This is less likely as it has not been recorded in Wales (1). The common name comes from the story that spiders living in Hampton Court would terrify Cardinal Wolsey (2).


Large house spiders take two years to reach maturity, emerging from the egg sac in late spring and grow to about half-size by the following winter, during which, in most habitats, growth ceases as the food supply dwindles. In spring growth is resumed, with males maturing in July/August and females in September/October. In early autumn males go in search of females, and it is this time of year when these species are most noticeable, running across carpets and falling into sinks and baths. A male finds a female close to maturation and guards her until she undergoes her final moult. Mating then takes place on the female’s web after preliminary bouts of palp-tapping and abdomen-bobbing by the male. Afterwards the male continues to co-habit with the female, mating repeatedly, until he eventually dies. The female overwinters with stored sperm and the next spring produces a succession of egg sacs, each containing c. 40 to 60 eggs (3).

The word 'spider' derives from the Old English word 'spithra', which means 'spinner' (3). Today a great deal of research is underway in identifying ways in which engineered so that it can be replicated, however spider webs have been used to heal wounds and staunch blood flow for many years. 
I like to try and learn and understand the etymology of names. The following has been defined by the British Arachnological Society (2). 

Tegenaria - Latin ‘teges’, a mat; Latin ‘arium’, a place (referring to the sheet web); saeva - Latin ‘saevus’, cruel or savage; gigantea - Latin ‘giganteus’, of the giants, huge; duellica - Latin ‘duellicus’, warlike.

1: Roberts, M.J. (1996) Collins Field Guide Spiders of Britain and Northern Europe.
2: British Arachnological Society. http://wiki.britishspiders.org.uk/index.php5?title=Tegenaria_spp.
3: Encyclopaedia of Life (EOL). http://eol.org/pages/1200102/overview

Thursday, 9 January 2014

BTO Early Bird Survey

I took part in there BTO Early Bird Survey this morning. The purpose of the survey is to build on observations from the Shortest Day Survey, and will investigate what effect, if any, light and heat pollution have on the feeding patterns of birds during a cold winter’s morning. The BTO Shortest Day Survey took place on 21st December 2004 and was promoted by BBC Radio 4 via the Today Programme. Some 5,460 responses were received from participants and these were used to determine patterns in the arrival of birds at garden feeders. The pattern of arrival, on average, was:



The BTO researchers then examined the arrival patterns in relation to a number of factors, including relative eye size and local habitat, in order to establish whether there was anything that determined when birds first arrived at feeding stations. They found that there was a negative correlation between eye size and time of arrival at garden feeders across species, and that this relationship remained significant when body mass was taken into account. This suggests that the time at which garden birds begin to forage on winter mornings may be limited by their visual capability at low light intensities.
They also found that birds appeared at garden feeding stations later in the morning in urban areas than in rural areas during winter. This supports the hypothesis that heat pollution may reduce overnight energy costs in small birds in urban areas, thereby reducing the urgency for them to 'refuel' first thing in the morning. Further information on the Shortest Day Survey can be found on the BTO report on-line at http://www.bto.org/volunteer-surveys/gbw/about/background/projects/shortest-day-survey

Preparation for this mornings observation involved identifying the number of street lamps within a 50m radius of garden, so using a great website at http://www.freemaptools.com/radius-around-point.htm, I was able to draw a radius around the house. This gave me a total of 4. Two near the back garden where the feeders are, and two in the front of the house.  I also had to measure the minimum and maximum temperature overnight.

So what happened this morning then. Well I made myself comfortable at the kitchen window while still dark and about 45 minutes before the scheduled sunrise, as predicted by the BBC weather page. Thus armed with a cup of tea (absolutely essential), the binoculars (not so essential, as the feeders are quite close) I was ready! It was a dark morning after the heavy rain last night, and because it was still heavily overcast. A male blackbird was the first to arrive, almost as soon as it was possible to see the feeders, and way before the scheduled sunrise, followed by a robin. The collared doves and jackdaws paid only a cursory visit, and seemed more intent on sitting the the Rowan tree "having a good chat" with their respective partner. All of the other smaller birds made fleeting visits to the feeders, primarily because the the robin patrolling the immediate area and chasing off anything smaller than itself. The results from this survey can be found on BTO website http://www.bto.org/volunteer-surveys/gbw/about/background/projects/early-bird-survey


I had a quick look at the BTO website to compare my observation with the others that had been submitted by al the other citizen scientists involved. Like my observation, the blackbird and robin were the first to appear in almost all the observations submitted. However, the smaller birds arrived earlier to the feeders than in my garden. I wonder if the aggressive robin is having any influence on this. I think I'll follow this up with other observations later in the year.