What are the brightest examples of communication in the animal kingdom?
Spiders are air-breathing arthropods that have eight legs and chelicerae with fangs able to inject venom. They are the largest order of arachnids and rank seventh in total species diversity among all orders of organisms.
These people's concerns come from a widespread and surprisingly uniform set of assumptions and "general knowledge" about spiders. And almost all of this widespread spider information is false!
- Spiders are arachnids, not insects.
- Other members of the arachnid family include scorpions, mites, ticks and harvestmen.
- Spiders have 8 legs while insects have 6.
- Spiders don't have antennae while insects do.
- Spiders are found on every continent of the world except Antarctica.
- The silk is a liquid inside the spider’s abdomen. When the spider releases it, it becomes solid and forms a thread.
- Some spiders eat their old web before starting a new one. Others roll the old web up and throw it away. Web spiders rebuild their web each day!
- Spiders don’t usually eat their prey because they have small mouths. Instead, they put chemicals into and on the prey to turn the body into a liquid. Then the spider sucks it up.
- The hair on a spider’s first pair of legs are sensitive to taste. The spider “tastes” its prey by touching it.
- Spiders use muscles to move their legs inward toward their body. But they don’t have muscles to pull their legs out. So to move legs out, a spider has to pump body water into each leg. This is why you can sometimes see a spider curled up – he has lost too much water to push his legs out again.
- Some spiders, such as the tarantula, are considered a low-maintenance pet.
Anyway, spiders belong to the Class Arachnida, insects to the Class Insecta. Arachnids are as distant from insects, as birds are from fish. It really is not a trivial distinction!
Black widow spiders have a red hourglass figure on the belly.
This hourglass is designed to indicate birds, a main predator of spiders, which are not safe to eat. (As bright colors tend to do)
Dr. Nick Brandley proved this by placing almost perfect models of black widows around a set of bird feeders, in artificial cobwebs.
Some of the widows had red hourglasses, others did not.
His team noted that birds were three times more likely to approach black widows without an hourglass than those with an hourglass. And that even when the birds approached the black widows who had that red hourglass, they often noticed it suddenly, they got scared and left.
But how can a black widow point this to birds when she lies on a horizontal web?
Now you know why black widows hang upside down on their spider webs.
But here is the second problem. If a spider has a bright red hourglass in its belly, how do you avoid frightening the insects you want to hunt?
Evolution, through its endless iterations, recognized that insects see in a different spectrum than birds, which see orange and red colors better. The red hourglass in your belly looks twice as dim for insects, and the color is much less likely to scare them, since that tone tends to blend more with the spider's body.
In addition, the hourglass in his belly, particularly when bright and large, is very attractive to males, which will be eaten after mating (as a source of protein. The life expectancy of a male is only 2-3 months , vs 3 years for females).
The communication of this hourglass is quite bright: repellent for enemies, invisible for prey, attractive for the opposite sex.
