Is It an Insect or a Spider?

Spiders and insects are not the same.  Even though we often refer to them both as 'bugs' and they are both arthropods, spiders and insects are actually two different species.  Spiders are classified as arachnids.  They are in the same family as scorpions, ticks, and mites.  Insects have their own classification, however.  There are a lot of different insects such as flies, bees, beetles, ants, etc.  How can you tell whether a 'bug' is a spider or an insect?  It can be confusing if you aren't sure what to look for.  Read on to learn how to tell the difference between the two!

What is the difference between an insect and a spider? They are both arthropods and we call them both bugs... but spiders and insects are two completely different species. When looking at a 'bug' and trying to figure out if it's an insect or a spider, you need to look at the number of legs, body segments, eyes, and appendages. Read on to learn more about how to identify insects and spiders. #kellysclassroomonline
(This is an updated version of a blog post I wrote in 2016.)

Learn to tell the difference between spiders and insects by looking at their legs, eyes, body segments, extra appendages and how it eats.  #kellysclassroomonline

When looking at a 'bug' and trying to figure out if it's an insect or a spider, there are a number of things on its body to look at.  You need to look at the number of legs, body segments, and eyes.  Does it have any extra body appendages?  These are the details that will help you figure it out.

Number of Legs

  • Spiders have eight jointed legs.
  • Insects have six jointed legs.  The back legs on some insects look different than the others because those legs are meant to help the insect jump.

Learn to tell the difference between spiders and insects by looking at their legs, eyes, body segments, extra appendages and how it eats.  #kellysclassroomonline

Number of Eyes

  • Spiders have eight 'simple' eyes.  Simple eyes only have one lens.
  • The number of eyes insects have can vary.  Some insects only have two eyes, whereas other insects can have five.  Also, insects have two 'simple' eyes and even more 'compound' eyes.  Compound eyes have lots of little lenses on them.  

Learn to tell the difference between spiders and insects by looking at their legs, eyes, body segments, extra appendages and how it eats.  #kellysclassroomonline

Body Segments

  • Insects have three body segments: the head, thorax, and abdomen.
  • Spiders have two parts: the abdomen and cephalothorax.  The spinnerets that spiders use to spin webs are in the abdomen.

Learn to tell the difference between spiders and insects by looking at their legs, eyes, body segments, extra appendages and how it eats.  #kellysclassroomonline

Extra Appendages

  • Spiders have chelicerae that look like fangs.  These chelicerae are often venomous.
  • Insects have antennae on their heads.  These antennae help them feel, taste, and smell.
  • Most insects have wings... but spiders never do.

Learn to tell the difference between spiders and insects by looking at their legs, eyes, body segments, extra appendages and how it eats.  #kellysclassroomonline

How They Eat

  • Insects can chew their food.  Spiders can't.
  • Spiders have to digest their food externally.  They use enzymes to liquefy their prey and use pedipalps to get it into their mouths.
  • Spiders are also predators... they hunt insects for food!

Learn to tell the difference between spiders and insects by looking at their legs, eyes, body segments, extra appendages and how it eats.  #kellysclassroomonline

Quiz time!  Is this beautiful 'bug' an insect or a spider?

Learn to tell the difference between spiders and insects by looking at their legs, eyes, body segments, extra appendages and how it eats.  #kellysclassroomonline

What about this spiky 'bug?'

Learn to tell the difference between spiders and insects by looking at their legs, eyes, body segments, extra appendages and how it eats.  #kellysclassroomonline

Are you confused?  Maybe this Youtube video by the Milwaukee Science Museum can help you.



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