Differences Between Spiders & Insects

More than a million known and documented insects live around the world, from the hottest temperatures in Africa to the frozen lands of Antarctica. The types of spiders are also vast and varied, although there are nowhere near as many of them --- 42,000 --- as there are insects. Although spiders and insects look similar and many people tend to group them under the same broad heading, spiders actually belong to a different scientific family than insects --- the arachnids.

  1. Structural Differences

    • Spiders have eight legs, while insects typically have six. The spider's body is divided into two regions: the cephalothorax and abdomen. The body of an insect is divided into three regions: the head, thorax and abdomen. Insects have antennae, while spiders do not. Insects have either two, four or no wings, while spiders never have wings. Spiders generally have eight eyes; insects have a compound structure with two eyes. The mouth of the spider is chelicerae shaped --- it has fangs; the mouth structure for insects is a mandible or jaws.

    Feeding Habits

    • Spiders are predators that feed on meat; the main source of their food is insects. Spiders are actually considered beneficial because of the number of insects they prey on. This includes a number of pest species, so spiders in a garden are quite useful. Insects eat just about anything, but mostly they feed on plants. Some insects like the praying mantis feed on other insects. Others, such as mosquitoes, feed on blood, and some indoor insects feed off anything they find on the floor.

    Silk Production

    • All spiders produce silk throughout their entire lifetime, although not all spiders build webs. Only a few insects produce silk, and then only at specific times during their life cycle. Beyond building webs and other types of snares, spiders use their silk to make egg casings, refuges and drag lines. Young spiderlings produce silk through a process called balloningin. The silk they produce is shot into the air and gets carried away by the wind.

    Reproduction

    • Spiders reproduce sexually, and fertilization is an internal process done indirectly. The male has to spin a small sperm web that it ejaculates. Males use elaborate courtship rituals to avoid being eaten by the female spider. They identify the spider species and sex by smell. Female spiders spin silk egg casings and lay thousands of eggs. Baby spiders or spiderlings pass the larval stages in the egg before being hatched. For insects, the reproduction process begins with sex that is similar to animal sex. Most insects require direct contact between a male and female for mating.