ENTOMOLOGY 2040 SECTION III INSECT STRUCTURES - EXTERNAL

LEARNING OBJECTIVES OF SECTION

After completing this section students should be able to:

• Describe the basic external structure of an insect.

• Explain why insects have an exoskeleton rather than an endoskeleton.

• Describe the three basic regions of insects and their function.

• Describe the basic structure of the head and its associated parts, and their function.

• Describe the various types of mouthparts found in insects.

• Describe the basic structures of the thorax and its appendages, and their function.

• Describe the basic structures of the abdomen and its associate structures, and their function.

 

Terms: Epidermis, sclerite, tagma, labrum, labium, maxilla, mandible, antennae, ocelli, compound eye, femur (and other leg segments), haltare, direct flight muscles, ovipositor, elytra, hemielytra.

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A. External Anatomy Structure.

     INSECTA, class in phylum ARTHROPODA.

        1. All arthropods have:

            a. Segmented bodies.

            b. Jointed appendages.

            c.) Bilateral symmetry.

            d. Chitinous exoskeleton.

        2. Insects also have:

            a. 3 body regions.

            b. 3 pair of legs.

            c. 1 pair of antennae.

        3. Characteristics of exoskeleton and endoskeleton.

            a. Exoskeleton provides:

               1) Support.

               2) Muscle attachment.

               3) Body covering (good protection).

               4) Water conservation.

               5) Growth restrictions (problem).

               6) Good mechanical advantage.

               7) Endoskeleton provides:

                    In comparison: ??

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        4. Insect body regions (tagma) and functions:

            a. Head, perception, food intake.

            b. Thorax, locomotion, food processing.

            c. Abdomen, reproduction, excretion.

        5. Head.

            a. Antennae.

            b. Eyes.

            c. Mouthparts (types).

            d. Chewing.

              1) Labrum.

              2) Mandibles.

              3) Maxillae.

              4) Labium.

            e. Chewing-Lapping.

            f. Siphoning.

            g. Piercing\Sucking.

            h. Sponging.

            i. Cutting\Lapping.

        6. Thorax.

            a. Legs.

            b. Wings.

            c. Indirect Flight Muscles.

            d. Direct Flight Muscles.

        7. Abdomen.

            a. Non-reproductive appendages.

            b. Cerci.

            c. Reproductive.

            d. Males

            e. Females

STUDY QUESTIONS

1. Describe the differences between the exoskeleton and the endoskeleton.

2. What are the major advantages of the exoskeleton? The disadvantages?

3. List the different types of mouth parts found in insects and give an example of an insect group that has each type.

4. What is a tagma?

5. Describe the two basic types of flight muscles and explain how they differ.

6. What is the function of the haltare? With what insect group is it associated?

7. List the different types of legs found in insects and give one example of an insect group that has each type.

8. How can some insects flap their wings faster than nerve impulses can fire?

9. What is an ovipositor? In what ways can it be used?

10. What is an aedaegus?

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