Download I. Introduction to Course

Entomology, Lecture 1: Introduction/body plan
April 3 & April 5 (part), 2006
I.
Introduction to Course
A.
Introduction of course members
B.
Course Philosophy
C.
Assignments/grading/etc...
II.
Significance of Class Insecta
A.
Numbers
1.
About 75% of all species of organisms are animals.
2.
97% of animals are invertebrates
3.
75% of invertebrate species are Arthropods
4.
Almost 90% of arthropod species which have been described are
insects (around 800,000 described species.)
 So, around 50% of all described species are insects!
5.
Estimates of between 5-30 million species of insects.
B.
Ecological importance
C.
Human issues
III.
The Insect Body: An Overview
A.
Exoskeleton/related integumentary structures: The arthropod exoskeleton,
with it strength, flexibility, and waterproof characteristics, contributed greatly
to the success of the arthropods, and especially of the insects to live
terrestrially.
1.
Epidermis
a)
Structure/function, general (Fig. 2.1)
b)
Dermal glands (structure/function)
2.
Cuticle
a)
Procuticle: contains chitin

Chitin

Overview

Some human uses for chitin and chitosan

Endocuticle

layers

resorbed during molt

Exocuticle

Often scleratinized (tanned proteins)

Not dissolved during molting, cast off.

Not always present
b)
Epicuticle: no chitin.

layers
3.
Coloration
a)
Pigments
b)
Structural coloration
4.
Molting (Fig. 2.5)
a)
Steps of molting process
5.
B.
Sclerites and conjunctiva (joints)
Insect Body Plan: Composed of segments organized into tagma (Fig. 2.10)
*Some of the terminology follows vertebrate anatomy. Not homologous,
though...
1.
Head
a)
Cranium
b)
Cervix
c)
Tentorium
d)
Compound eyes
e)
Ocelli
f)
Antennae
g)
Mouthparts

labrum

hypopharynx

mandibles

maxillae

labium
2.
Thorax
a)
General structure
b)
spiracles
c)
legs (and specific parts of legs)
d)
wings (basic structure)
3.
Abdomen
a)
General structure
b)
Final segment

3 plates (epiproct and paraprocts)

has paired cerci (homologous with legs, mouthparts)
c)
External reproductive structures

Female: ovipositor and gonopore

Male: penis usually on 9th abdominal segment
Study questions
1.
Approximately what percentage of living organisms are insects?
2.
Briefly list a few key ecological roles of insects.
3.
List and briefly describe six functions of an arthropod’s exoskeleton.
4.
One of the functions you should have listed above is “protection”. In what ways is the
exoskeleton protective? You should be able to list at least four specific things.
5.
Make a simple sketch of the exoskeleton and label the key layers and parts (epidermis,
dermal glands, endocuticle, exocuticle and epicuticle).
6.
What is the major function of the epidermis?
7.
What types of substances are secreted by the dermal glands (should be able to list at
least three specific substances), and how do these substances reach the outer surface of
the exoskeleton?
8.
What specific molecule makes up the bulk of the exoskeleton? Is it a protein,
carbohydrate or lipid?
9.
Describe the key differences between the exocuticle and endocuticle. Which one is
absent in the joints?
10.
What is the function of the cement layer of the epicuticle? What is the function of the
superficial (wax) layer of the epicuticle?
11.
Describe, step-by-step, the process of molting.
12.
Provide a brief definition of the following insect parts:
a.
Tagmata
b.
Tentorium
c.
Ocellus (pleural: ocelli)
d.
Spiracle
e.
Ovipositor
f.
Prothorax
13.
On which segments are an insect’s legs found?
14.
On which segments are an insect’s wings found?