Order Araneae: Definition, Characteristics & Life Cycle

Instructor: Sarah Friedl

Sarah has two Master's, one in Zoology and one in GIS, a Bachelor's in Biology, and has taught college level Physical Science and Biology.

Spiders are more than just the creatures you find in your house. In this lesson we'll discuss what spiders are, what they look like, where they live, and their reproduction and life cycle.

Don't Bug Me!

You've seen them, movies have been made about them, and if you have arachnophobia you're terrified of them. But what do you really know about spiders? These eight-legged animals are often mistaken for insects but they're actually cousins of scorpions, ticks, mites, and harvestmen. Together, these animals make up the class Arachnida. Arachnids are part of the phylum Arthropoda which, simply put, is HUGE. Famous arthropods include crustaceans, millipedes, insects, and of course, spiders and their kin.

Habitat, Diet, and Characteristics

Specifically, spiders make up their own order within Arachnida called Araneae. Like other arachnids they have eight legs (insects have only six), and they also have either six or eight eyes as well as two body segments (insects have three). The first is a fused head and thorax called the cephalothorax, followed by the abdomen which is where all those legs are attached. Found on the cephalothorax are the spider's mouth, fangs, and two pedipalps which are leg-like structures used to grab and hold onto prey.

Spiders have 6 to 8 eyes, which are quite interesting looking!
spider eyes

Spiders are found on every continent except Antarctica, and world-wide there are about 40,000 known species though it is believed there are many more that haven't yet been described. Spiders come in many different sizes and colors. The smallest spider is the orbweb spider, which is just over one hundredth of an inch long or about the size of a pinhead. The largest spider is the goliath bird-eating tarantula, which can be over a foot across with inch-long fangs! Some, like the elaborately decorated peacock spider are brightly colored with very distinctive markings, while others, such as the dangerous brown recluse spider have a duller, more 'earthy' coloring. Female spiders tend to be larger than males, and while most spiders have venom the majority are harmless to us.

Coming in at over a foot across, the goliath bird-eating tarantula is the largest spider
goliath bird eating tarantula

Spiders are predators and have a significant impact on insect control. Not only do they keep the insects at bay in your own house, but they are so good at eating insects that they are used for insect control for a number of crops. Spiders have some cool tricks up their sleeves, too. For example, in addition to venom, the spitting spider secrete a sticky substance that glues their prey down. Spiders also make silk with which they weave their webs. Some spiders can even make several different kinds of silk for different purposes. For example, the orb weaver produces at least seven types of silk for capturing prey, producing egg sacs, spinning webs, and more.

Peacock spiders are elaborately and brightly colored
peacock spider

Spider Life Cycle

Spider reproduction differs among species and is not entirely understood. Males will place their sperm on the web, which will then get transferred to the female for fertilization. In some species, the female spider eats the male spider after mating. In other species, females die after laying their eggs, which may be anywhere from dozens to thousands. Some spider moms not only live after laying eggs but will also invest in her babies and provide a great deal of care.

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