Donnie Severs, age 11, of Des Moines, Iowa, for his question:
In what group do the spiders belong?
We are told that spiders are not insects. This is true because of basic physical differences, such as an extra pair of legs. However, spiders and insects are cousins, once or twice removed. Both belong in the enormous phylum Arthropoda, which means the animals with jointed feet. The bodies of arthropods are encased in jointed exoskeletons. This feature makes them different from all other creatures.
A spider is an arthropod, with no internal skeleton. Her soft insides are packed neatly in two sacks, which form her outside exoskeleton. Her head and chest sections ale united to form her cephalothorax, which is stashed inside a shield called the carapace. Her round abdomen is held in a bulging bag of leathery skin.
Almost 30,000 known spiders belong in the Arthorpoda phylum, plus another 20,000 or so still waiting to be discovered. The next stage of scientific sorting separates the spiders from the insect arthropods. It groups them with an assortment of scorpions and mites in the large class Arachnida named for a legendary maiden of ancient Greece. She was Arachne, famous among her friends as a spinner of fine fabric. Apparently their praises went to her head and the mortal Arachne grew bold enough to challenge the goddess Athene to a spinning contest.
The world watched as Arachne wove pictures of playful gods. The goddess was so enraged by the topic and so jealous of the exquisite tapestry that she tore it to shreds. The girl Arachne hanged herself in shame, or so they say, and the noble Athene recovered her usual dignity. To make amends, she changed the hanging rope into a fine silken thread and made Arachne into a spider.
All the spiders belong in the Arachnida group and it is safe to refer to any one of them as an arachnid. However, this group also includes many non spinning members of the phylum arthropoda. Hence, the Arachnida class is subdivided into several orders. The spiders and only the spiders belong in the order Araneida. The name of their group is borrowed from the Latin word for spider.
The Araneida order is subdivided into smaller family groups of similar spiders. One family includes the fascinating trap door spiders, another includes a group that spins funnel shaped webs in our cellars and attics. The furry fearsome tarantulas belong in the family Aviculariidae. Their family name means the bird spiders, because some of them steal fledgling birds from the nest.
The charming orb spiders that spin their cartwheel webs in the garden, belong in the family Argiopidae. Among them is a group of pretty colored spiders of the genus Argiope. Each member of the genus has her personal species name. The one we know best is the busy orange and black orb spider. Her official name is Argiope aurantia, meaning the golden one.