It’s time for the first creepy-crawly installment, and what better arthropod to start with than spiders? Arachnophobia (the fear of spiders) is one of the most common phobias. It has been estimated that 55% of females and 18% of males in Western countries suffer from this particular fear (http://webs.wichita.edu/depttools/depttoolsmemberfiles/psychology/publications/Wagener%20&%20Zettle%20Paper.pdf). Despite this widespread fear, spiders are critical to life on Earth. Without spiders, the world would quickly become overrun with insects. Even I, as much as I love insects, can see that this would be a huge problem!
Spiders belong to the Order Araneae. They are a very diverse group, but have several unifying characteristics. They have eight legs, two body regions, no wings, and no antennae. Their relatives include mites, ticks, Daddy long legs (harvestmen), and scorpions. All spiders also have spinnerets and fangs, and all spiders are venomous. Most, however, pose little or no danger to humans.
All spiders (with the exception of a recently discovered species, see here: http://news.bbc.co.uk/2/hi/8302535.stm) are predators. Spiders are well-known for their web-spinning finesse. Spider silk is a remarkable substance, being both strong and very flexible, and is the envy of scientists and engineers. While many spiders spin webs, others rely on stealth and speed to catch their prey, such as many tarantulas. The Bolas spider uses its silk in a very unique manner to catch prey. Check out this video to see its amazing hunting behavior: http://www.youtube.com/watch?v=2UfMJJAzvbI
Spiders have many fascinating courtship rituals. For males, finding a mate can be a dangerous business. A female may decide he would make a better meal than a mate. In general, female spiders are much bigger than males, so a male’s best bet is to make a hasty retreat if things take a turn for the worse. To try to avoid becoming snack food, male spiders employ different methods for alerting a female to his intentions. Some males will tap a certain pattern on a female’s web to let her know he’s not there to be dinner. Jumping spiders have particularly unique courtships. The male spider is usually much more colorful than his female counterpart, similar to many birds. He will perform a complex series of “dance” moves, accompanied by abdomen vibrations. Usually the female can’t help but be impressed! See here for a demonstration of a jumping spider courtship dance: http://www.youtube.com/watch?v=sUypt5lMYUo
After mating, male spiders die shortly after, either by being eaten or naturally. Some males will actually allow themselves to be eaten by the female to help ensure she will produce healthy babies. In any case, the female is on her own when it comes to their offspring. Female spiders are actually very good mothers. Some will capture prey, bury it, and then lay an egg sac on it so her babies (known as “spiderlings”) will have a meal waiting for them when they hatch. Certain tarantula mothers will time their death to coincide with the emergence of their offspring, and the spiderlings will then eat her. Other spiders, such as wolf spiders, will carry their egg sac until the babies hatch. The spiderlings will ride piggy-back on their mom for several weeks. Their mother will protect them and feed them until they are big enough to fend for themselves. Go here to see a video of a mother wolf spider with spiderlings on her back (I think it’s really cute!): http://www.youtube.com/watch?v=axDpsLPhYSg&feature=related
There’s much more to say about these amazing creepy-crawlies, so check back soon for part 2!