31.10.2010., nedjelja
WAY OF LIFE
 Fight-leggers in many variations When we talk about spiders, we have members of common spiders (Aranea) in mind. But, speaking more precisely, the Arachnids also include camel spiders, ricinlei and amblypygi, as well as acari, harvestmen, palpigradi, pseudoscorpions, scorpions and thalyphonida. Spiders are found all over the world. There are 4000 of spider species (aranea), and 1000 of them are found in Germany. The largest spiders live in tropical climate. Almost all spiders have habitat on the ground. The diving bell spider (argyroneta aquatica) is the only spider living in water. Several species hunt on water surface and in coastal areas. Most spiders are active during sunset and at night. Spiders have a lot of siblings! Reproduction is often dangerous for male spiders. If the female does not perceive a given male as the appropriate mating partner or if she is not ready to mate, this evidently small male can soon end up as prey. Sexually mature males have mating organs at the end oft he pedipalps called bulbus. The males fill bulbus with their own sperm. First they excert it into a specially designed web, and after that suck it into the bulbus. With the help of bulbus, the sperm can be safely transferred into the female genital opening during mating. Spiders lay eggs and cover it with their own silk for protection, until a more or less solid cocoon is formed. In some species, the female guard the cocoon or drag it along until hatching. Spiders jump out of their skin! Spiders have an outer skeleton (exoskeleton). Their body is not stabilized by bones, but by firm external envelopment. While their abdomen can expand when eating, the outer skeleton remains immovable. That is why spiders have to replace their skini n order to grow. This happens in different time intervals, depending on the spider species, its feeding possibilities and external factors. When replacing their skin, web-building spiders most often hang with their back legs to the thread for changing skin. Theraphosidae lay on their back. The old skin is taken off, revealing the already near-finished new skin, which is still soft and elastic. While it hardens, the new skin also expands and the spider grows. |
