27th March 2011 - Earthworms & Spiders

Worms - David Attenborough’s Life Stories from 25th March 2011 was about earthworms. Unfortunately, I don't have a permanent link to this podcast but there is some information available on youtube.

In Australia, there are giant earthworms, as thick as a thumb and 6ft long, although the longest is claimed to have been 13ft long!  However, they are extendable and breakable and thus difficult to measure accurately.

Earthworms are found on all continents except Antarctica where the frozen ground is too hard.

There are 200 species in Europe but  Britain only  has 26 species since all its native species were killed off in the Ice Age and only a few made it back before Britain and Continental Europe were separated. Although there are relatively few species in Britain, the ones we have are prolific and there can be as many as 50,000 worms in an acre.

At night, worms nibble on leaves and drag them back into their tunnels. When they find a leaf, they grip it with their mouth and drag it home.  They grip pine needles by the lower end, but most they grip by the stalk. To test the intelligence of worms, Darwin did an experiment with triangles of paper. The worms almost always pulled the triangle by the sharpest point having crawled all over it first, which does indeed show they are intelligent.

Worms can produce both eggs and sperm.  The yellow band around their bodies is necessary for their reproduction.  When two worms get together, they produce lots of slime covering both. They exchange sperm which they each keep in a pouch.  After a few days, the band produces more slime  which hardens into a ring. The ring travels up the body, collecting the other worm's sperm, takes it to the eggs, fertilises them and then takes them off the worm to form a capsule of fertilised eggs. It is unknown whether the large Australia worms reproduce in the same manner, although their egg capsules have been found as can be seen in the video linked above.

Spiders - Spiders encasing trees with webs has the advantage to us of capturing lots of mosquitoes!  In Pakistan, after flooding, the spiders were unable to make webs on grass and low lying bushes so thousands made for the trees. Even with all the lying water, there were few mosquito bites as they got caught in the webs in the trees.