Friday, 17 June 2011

Cool critter of the month: The orb web spiders

Many people don’t like spiders, 8 legs, lots of eyes, fangs and the potential to lay eggs in your ear while you sleep (slightly exaggerated perhaps...), but I think this group gets too much bad press. So I will offer some defence for the spiders, showing lots of pictures of spiders to people who hate them is unlikely to change their minds, so I have chosen a group that not only have beautiful colouration but also build some of the most fantastic webs of all our eight legged allies (against flies, who let’s face it are annoying).

Orb web spiders are common; some of the first webs that you ever saw as a child were most likely orb webs. I remember going out into my misty, dew covered back garden and coming face to face with one of these for the first time:

Simple elegant and beautiful the work of Metellina segmentata the common orb weaver.

Even building these (relatively) simple webs is pretty hard work:

Yet there are many more ticks that the orb weavers have up their sleeves, and the less common varieties make webs of all kinds of brilliant shapes and forms. The wasp spider is an EU and U.K. resident that are not content with a standard orb web; they like to mix it up with some flare. Zigzag decorative silk patterns are built into their webs. They also have the ability to take on bombardier beetles (who defend themselves with a spray of noxious boiling acid), by shooting silk countermeasures at them before the beetle comes into range for its own acid attack (Pokémon like battles can be imagined at this point).

Argiope bruennichi the wasp spider has stylish taste, and its attacks against bombardier beetles are super effective!

Not to be outdone, there are a range of other orb weavers of the family Argiope that also produce awesome web enhancements called stabilimentum. Here is a choice selection of their brilliant webs:

The aptly named St Andrews cross spider (Argiope keyserlingi) has a thing for Scotland, too bad it lives in Australia...

I couldn’t find an ID for this guy, short of being an Argiope. This issue is fairly common in spiders (not being an expert!) as many are virtually impossible to tell apart to species level without years of training. Nevertheless, very cool web decoration.

Again another unknown Arigope, but so pretty I couldn’t resist!

Argiope aurantia the writing spider goes nuts with its own central decoration

The orb weavers have more tricks up their sleeves than just fancy decorations in the middle of a web. They are also the masters of size and scale in web design as well as raw web power. The golden orb web spider, Nephila maculata builds webs that are stronger than Kevlar. Most people know the fact that spider web is stronger than steel gram for gram, that is nothing to the golden orb weaver. Their webs are large (2m or so) and strong enough to catch birds.

Raw web power at its best...

Indigenous people of the Solomon Islands used the nets for just this purpose, along with fishing lines and even bandages. The slightly golden covered webs have been looked at by scientists hoping to grow replacement artificial human ligaments and tendons to be used to treat chronic injuries. In addition, since it is stronger than Kevlar, military type chaps are also figuring out how to make spider web bullet proof vests (sign me up for a suit of golden spider armour!).

Another species of Nephila, N. Komaci holds the title of the largest orb weaving spider known to man. These guys were just discovered in South Africa in a local park after two scientists were kicking around on their lunch break. It builds giant webs over 6m in diameter, and like many spiders the female has the nasty habit of eating the male either after or during sex. Of course who could blame her, she has so many eggs to make and the male is less than 1/10 of her size (no more than a light snack).

This is just the webs of one group of spiders; there are whole hosts of other fancy webs out there. Many don’t have the elegance of the orb weavers, but I’m sure I can come back to them at some point in the future. Maybe some of these beautiful webs can even convince you to foster a bit of spider love...

One step at a time perhaps!

Thursday, 9 June 2011

My horoscope for today?

Some people claim to be able to predict minute details of our lives based on the positions of the planets at the times of our births; this is the practice of astrology. Every so often a piece of pseudo scientific bunk comes and gets right under my nostrils and wafts itself just long enough to cause my eyes to water. This results in me ranting to Bob (who sits next to me in the office) until he tells me that I should actually write something about such foolishness...this is the result.

I went online and downloaded 15 horoscopes for me (a Cancer if you must know) that makes some predictions about my emotional or physical state today (June 09, 2011). Now 15 isn’t a massive sample size, but more than enough for the tests that I am planning to do on the data. If I really wanted to prove this I would collect a few more horoscopes (to the critics out there).

Now from these datasets individuals were asked to rate how positive the predictions or assessments were. A score of 1 meant it was a bad day, hopelessness and despair reign; apparently I would be best just staying at home hiding from the world. A score of 5 meant that I have a brilliant day to look forward to; bunnies, rainbows (with pots of gold), romantic success and work brilliance. So now we have an index of how well each horoscope felt I would do on this one particular day. All horoscopes were constructed using the same system of Western Sun sign astrology (no Chinese zodiacs creeping in here, although it didn’t stop one from mentioning Ganeesha who is not responsible for any zodiac system) so should as such make similar predictions for my day. Well here are the results:

Not many 1’s but a pretty even mix of all of the other values. Is it different to a random selection of scores? I simulated 100 datasets of 15 values 1:5 using a uniform distribution, i.e. any one of the values were equally likely. I then compared these simulated (and totally random between 1:5) values with our list from a horoscope. The result was, no significant difference in the mean scores between these samples (p-value = 0.6, mean of the horoscopes= 3.4, mean of the randoms= 3.51). So there is basically no difference between making up a score for the horoscopes and the relative predictions they make.

At this point someone could jump in and say, ‘Well Mark! Horoscopes may well differ in how they present the information, but the core message is conserved.’ This could indeed lead to different emotional scores and yet have the same key message underneath it all. I also did a keyword analysis to debunk this. Keywords (such as fear, hate, success, opportunity, love, magnetism etc) were only repeated in two of the horoscopes. With fuzzy matching (happiness is the same as joy, hate the same as anger etc) this number only rose to 4. Indeed results ranged from predicting a monetary windfall from an aging relative to romantic success, accelerated mental processes (awesome!), oozing charm and all the way to serious emotional disturbances.

Four of the entries were directly contradictory, noisy and disturbed thoughts and difficulty concentrating was the exact opposite to sudden insights and enhanced mental processes. Equally brilliance at work was predicted by one website followed by patience and persistence required with a project going nowhere by another.

I say, go out and check for yourself, consistent records between individual horoscopes have shown time and time again that they are not consistent. If there was a genuine casual mechanism responsible for changes here on earth relating to planetary position, it would be measurable and testable. There could well be a mechanism by which gravity of foreign bodies affects our behaviour; it’s not beyond the realm of logic. The sun and moon do have measureable effects on human happiness, with suicide being directly related to day length (sorry Sweden). I am simply showing that current astrology does not hold to a meaningful method (it is not consistent) and fails to make testable predictions.