ENTM 307E���� - LABORATORY 1

 

What are insects and how do they feed?

(Web-users: Please use images for figures provided during the class period)

 

I. Learning objectives:

• Basic external morphology of insects
• Variation in external morphology associated with insect injury to plant

 

 

II. Basic Morphology

A. The Exoskeleton

The hardened skin of an insect is called and exoskeleton because muscles are attached to its inner surface. It� is composed of a layer of epidermal cells plus 3 secreted layers that make up the cuticle. Specialized cells in the epidermis can be associated with spines (setae) and glands that produce secretions.� The cuticle is generally rigid and makes up the external skeleton of the insect.� Each layer of the cuticle is chemically different.�

 

1.      Epicuticle- (outer layer) contains wax which makes the insect waterproof.

2.      Exocuticle- ( middle layer) contains sclerotin, a protein that hardens after molting and makes the cuticle rigid.

3.      Endocuticle- (lower layer) contains, chitin, a nitrogen containing� polysaccharide is firm but is more flexible.

 

 

 

B. Generalized Insect Structure.

 

Segmented Body

 

 

 

 

Functional insect sections (tagma)

The insect is divided into 3 sections, the head, the thorax and the abdomen. The head contains the mouth, eyes and antennae. The thorax is responsible for locomotion and contains the legs and wings.�� The abdomen contains reproductive and digestive organs and other appendages.�

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Find all parts labeled in this illustration of a generalized insect

 

 

 

 

 

 

 

 

3. Lubber Grasshopper Morphology�

1.� The Insect Head

����� ����� A.� Gross Morphology

Examine an insect head and find parts labeled in the figure.� Be sure to locate the compound eye and the ocelli.� While both these organs are responsible for sight, the compound eye sees more detail.

 

 

 

 

 

 

3. Lubber Grasshopper Morphology

1.� The Insect Head (contd.)

B.     Head Appendages

 

1. The Antenna.� Excise the antenna from its base (scape).� Indicate what type of antenna it has by taping it to the appropriate type in the figure.

C. Lubber Grasshopper Morphology

1.� The Insect Head (contd.)

C.    Head Appendages

2.� The Mouth-� Note how mouth appendages will vary in shape and function in the figure on page ___)

Excise the mouth appendages and tape them to the appropriate illustration. .

 

 

C. Lubber Grasshopper Morphology

2.� The Insect Thorax � This section is responsible for locomotion.

A.    The insect leg� - Insect legs are jointed. No insect has more than one pair of legs per segment.� Note how modifications of the insect leg are adapted to different functions in figure 2.15 (attached p.__).

 

Excise the insect leg at the coxa and tape it below.�

 

 

 

 

 

 

 

B.     The insect wing- Note how modifications may be characteristic of different insect groups in figure 2.15 (attached p.__)

 

1.      �Excise the leathery forewing and tape it below.

 

 

 

 

 

 

 

2.      �Excise the membranous hind wing, spread it and tape it below.

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C. Lubber Grasshopper Morphology

3.� The Insect Abdomen � This section is responsible for digestion and reproduction.�� Please take note of the following items:

 

A.    �The spiracles.� These are the organs through which insects breath.�

 

 

 

B.     The insect cerci.� This sensory organ helps insects detect when they are being pursued.� Touching a the cerci of a live insect will usually cause it to flee.

 

 

 

C.    The insect ovipositor.� This is the organ that females use to deposit eggs,- Note how modifications of the insect ovipositor are adapted to different functions in figure 2.17 (attached p.__).

 

 

 

 

 

III. Review Questions.

 

Name the 3 insect functional segments (tagma).

 

How many legs does an adult insect have?

 

In what ways can insect appendages be modified to adapt to different functions-?

����������� (focus on legs and ovipositors)

 

Name the 3 layers of the insect exoskeleton and discuss their chemical differences.