ENTOMOLOGY 2040 SECTION V INSECT SENSES

After completing this section students should be able to:

• Describe the general types of stimuli that insects perceive.

• Describe the various structures that insects use to hear and the range of sounds that they can perceive.

• Explain how insects are able to perceive chemicals through taste and smell and describe the sensitivity levels they have.

• Explain how insects are able to perceive mechanical stimuli like touch and vibration through their exoskeleton.

• Describe the components and function of the compound and simple eyes.

• Explain how the color vision of insects differs from that of humans.

• Explain how insects are able to walk and perform other functions without a head.

• Describe the function of the insect brain and compare that to the function of the human brain.

Terms: Ocelli, synapse, sensilla, tympanic organs, chemoreceptors, ommatidium, giant axons, compound eyes, ommatidium, stemmata, apposition eyes, rhabdom, olfactory receptors, hygroreceptors, mechanoreceptors, flicker fusion frequency.

Insect Senses. Five Basic Categories.

Visual receptors, Sound receptors, Chemoreceptors (odors and taste). Hygro receptors (humidity), Mechanoreceptors (body deformation).

    1. Visual receptors. Insects see.

            a. Light vs. dark.

            b. Form - shapes.

            c. Movement.

            d. Distance.

            e. Colors.

            f. Polarized light.

Visual Structures.

               • Light receptive cells in exoskeleton, ( maggots).

               • Ocelli (structural complexity varies) photoperiod perception.

                • Compound eye (many eye units). Structures of ommatidium.

Shape Perception. Not good, different basis "flicker fusion frequency".

Movement Perception. Very good. Stimulation of different eye units.

Distance - predators.

Color perception. Differences.

        Bees see fewer colors (4 vs. 60).

        Bees visual range shifted to short end of spectrum.

    2. Sound.

        a. Perceive air pressure changes.

            (1) Hearing structures

               • Tympanic membranes - (hoppers).

               • Hairs - male mosquitoes.

               • Sensitivity.

                (a) Humans 15 - 20,000 c/sec
                (b) Moths 30,000 - 80,000
                (c) Hear bat sonar
                (d) Hoppers >100,000

               • Sound production.

    3. Chemoreception.

        a. Taste Receptors.

            (1) Mouth parts.

            (2) Tarsi of some flies, bees.

        b. sensitivity to materials - (like humans)

            (1) Salt, sweet, sour, bitter.

            (2) Levels perceived differs.

        c. Smell (olfactory sense).

            (1) receptors generally on antennae (enlarged club).

            (2) sensitivity, high

    4. Hygro receptors.

        a. Good perception of humidity.

        b. Poorly understood. ?? "hair" and evaporative cooling?

    5. Mechanoreceptors.

        a. Body orientation perceived by modified setae (hairs).

STUDY QUESTIONS

1. How does the ability of insects to perceive the electromagnetic spectrum (color) compares with humans?

2. Discuss the concept of co-evolution in regard to the development of flowering plants and pollinating insects. How does vision of insects plays a role in this co-evolution.

3. How do insects measure distance. How does this differ from the process used by humans? Why is this ability important to insects?

4. Describe the various structures used by insects to hear sounds. What are some ways that the ability of insects to hear differs from that of humans? How do some insects use hearing in self defense?

5. Why do you think some female insects eat the male during, or after copulation? What would be the evolutionary value of that behavior?

Go to Section VI - Insect Behavior