Chapter 18: From Sponges to Invertebrate Chordates


This may look like a scary creature from your worst nightmare, but it wouldn’t hurt a fly. In fact, it is a fly! The picture shows the charming portrait of a horsefly, up close and personal. Those big, striped, colorful orbs are its eyes. Did you ever look through a kaleidoscope? If so, then you have an idea of what the world looks like to a horsefly.

What other organs do insects like this horsefly have? Besides sensing their environment, what other functions do their organs serve? In this chapter, you will find out. You will read not only about fly eyes. You’ll also read about octopus ink, spider fangs, and other fascinating features of invertebrates.

Chapter Outline

18.2 Mollusks and Annelids

18.3 Arthropods and Insects

18.4 Echinoderms and Invertebrate Chordates

Opening image copyright Mikhail Melnikov, 2010. Used under license from

For first Table in chapter 18, from top to bottom:

For second Table in chapter 18, from top to bottom:

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