1. INTRODUCTION TO THE STUDY OF ARTHROPODS
CPT 201
INTRODUCTION TO THE STUDY OF ARTHROPODS

2. Module One INSECTS AND THEIR ALLIES
Content
ENTOMOLOGY (INSECT SCIENCE)
PHYLUM ARTHROPODA

3. Entomology is a basic and applied science that is dedicated to the study of insects and other related arthropods.
The study of insects helps us better understand
How to protect our crops, livestock and properties from harmful insects
How to protect and conserve insects that are beneficial to man
Other animals including man

4. STRUCTURAL ENTOMOLOGY
CAREER OPPORTUNITIES IN ENTOMOLOGY
AGRICULTURAL ENTOMOLOGY
MEDICAL ENTOMOLOGY
TAXONOMIC ENTOMOLOGY
STRUCTURAL ENTOMOLOGY
MILITARY ENTOMOLOGY
VETERINARY ENTOMOLOGY
FORENSIC ENTOMOLOGY

6. were more closely related
Among the mandibulates, insects have traditionally been set apart from the crustaceans, and grouped instead with the myriapods (centipedes and millipedes)
In recent years, a mass of accumulating morphological and molecular data have shown that insects
were more closely related
to crustaceans than to any other arthropod group.

7. Subphylum Trilobitomorpha Subphylum Chelicerata Subphylum Atelocerata
PHYLUM ARTHROPODA
Subphylum Trilobitomorpha
Subphylum Chelicerata
Subphylum Crustacea
Subphylum Atelocerata

8. Myriapods Subphylum Atelocerata (Mandibulata) Class Chilopoda
Class Diplopoda
Class Hexapoda or Insecta
Myriapods

9. Super Order Apterygota e.g. silverfish
Class Insecta
Subclass Ectognatha
Super Order Apterygota e.g. silverfish
Super Order Pterygota
Subclass Entognatha
e.g. springtail

10. Super Order Pterygota
Exopterygota
Endopterygota

11. Stick insect Preying Mantid May fly Grasshopper Dragon fly
EXOPTERYGOTA
Order Ephemeroptera
Order Odonata
Order Orthoptera
Order Phasmida
Order Mantodea
Stick insect
Preying Mantid
May fly
Grasshopper
Dragon fly

12. Stink bug Termite Louse Ear wig Stone fly Cockroach EXOPTERYGOTA
Order Blattaria
Order Isoptera
Order Dermaptera
Order Plecoptera
Order Phthiraptera
Order Hemiptera
Stink bug
Termite
Louse
Ear wig
Stone fly
Cockroach

13. Endoptery-gota Lacewing Scorpion fly Housefly Honey Bee Butterfly
Order Hymenoptera
Order Neuroptera 
Order Coleoptera
Order Mecoptera
Order Siphonaptera
Order Diptera
Order Lepidoptera
Lacewing
Scorpion fly
Housefly
Honey Bee
Butterfly
Beetle
Flea

14. Success of Insects as a Group
Efficient water conservation methods
Ability to consume different kinds and qualities of food.
High adaptive capacity
Possession of an Exoskeleton
Dispersability by air current
Exhibition of metamorphosis
Smallness of size
Capacity of flight

15. EXTERNAL STRUCTURE OF AN INSECT
MODULE TWO
EXTERNAL STRUCTURE OF AN INSECT
Content
THE INSECT’S CUTICLE
BODY SEGMENTATION
BODY REGIONS

16. THE INSECT’S CUTICLE
Unlike vertebrates, insects have no backbones. Instead, they have a tough outer support framework or exoskeleton called cuticle.
The cuticle of each segment is formed into several hardened plates called sclerites, separated by infolds (sutures), which give it flexibility.
The sclerite covering each segment is divisible into 4 main parts, namely,
a dorsal region or tergum,
a ventral region or sternum and
on either side, a lateral region or pleuron.
The uppermost layer of the insect cuticle is waxy in nature; it controls water permeability and prevents desiccation.

17. THE INSECT’S SEGMENT

18. BODY SEGMENTATION
The insect’s body is divided externally into a series of segments separated by inter-segmental membranes.
The insect body comprises twenty (20) primitive segments, all of which may be apparent in the embryo. These segments are grouped into well defined regions – the head, thorax and abdomen.
The grouping of body segments into distinct regions is known as tagmosis or tagmatization. Each body region is referred to as a tagma (Plural: tagmata).

20. The head is made up of 6 segments and an anterior non-segmental acron that have all fused together into a hard case or head-capsule.
The thorax consists of 3 segments, each of which carries a pair of legs. The 2nd and 3rd segments each carry a pair of wings. The thorax is connected with the head by the cervix or neck.
The abdomen comprises 11 segments and a terminal non-segmental telson.

21. THE HEAD AND ITS APPENDAGES
The head tagma is highly sclerotized to from a hard capsule or cranium.
The head articulates with the thorax through the neck or cervix.
The insect head consists of several sclerites and sutures
The appendages of the head are called Cephalic appendages
Functions of the insect head include – food ingestion, sensory perception, coordination of body activities and protection of the coordinating centres.

22. SCLERITES AND SUTURES ON A MANDIBULATE’S HEAD

23. TYPES OF INSECT HEAD
PROGNATHOUS
HYPOGNATHOUS
OPISTHOGNATHOUS

24. SOME CEPHALIC APPENDAGES
INSECT ANTENNAE

25. SOME MODIFICATIONS OF THE INSECT’S ANTENNAE
They are primarily used as organs of smell, but in some insects they may serve additional functions

26. CEPHALIC APPENDAGES B. INSECT MOUTHPART
The insect mouthpart consists of the labrum, mandibles, maxilla and labium.
Functionally speaking, the insect’s mouthparts are of two main types namely –
Mandibulate (chewing): grasshopper, cockroach
Haustellate (sucking): This could be
a. Piercing-sucking mouthparts: aphids, mosquitoes
b. Siphoning mouthparts: butterfly, bee
c. Sponging mouthparts: housefly

27. MOUTHPART OF A TYPICAL MANDIBULATE

29. THE THORAX AND ITS APPENDAGES The prothorax does not bear wings.
The thorax is made up of three consecutive segments namely the prothorax, mesothorax and metathorax.
Each of these segments bears a pair of legs. When the mesothorax and metathorax each bear a pair of wings
The prothorax does not bear wings.
The segment of the thorax is made up of four body plates (sclerites)namely a dorsal body plate (Tergum or Notum), a ventral body plate (Sternum) and 2 lateral plates (Pleura).
Function of the insect thorax is LOCOMOTION

31. INSECT LEGS AND THEIR MODIFICATIONS
THORACIC APPENDAGES
INSECT LEGS AND THEIR MODIFICATIONS
Insects characteristically have three pairs of jointed legs on thoracic segments.
Each leg has six major components: coxa , trochanter, femur , tibia , tarsus , and pretarsus (from proximal to distal).
The femur and tibia may be modified with spines. The tarsus appears to be divided into one to five "pseudo-segments" called tarsomeres.

32. Divisions of a typical insect leg

33. Like the mouthparts and antennae, insect legs are highly modified for different functions, depending on the environment and habit of the insect.
Ambulatory legs: are used for walking. Examples: Bugs
Cursorial legs: They are modified for running. Examples: Cockroaches, ground beetles.
Saltatorial legs: are hind legs adapted for jumping. Examples: Grasshoppers, crickets.
Raptorial legs: are fore legs modified for grasping preys. Examples: Mantids, ambush bugs
Fossorial legs: are fore legs modified for digging. Examples: Mole crickets and cicada nymphs.
Natatorial legs: are modified for swimming. Examples: Aquatic beetles and bugs.
Foragial legs: Legs of honeybee are adapted for various functions

34. FOSSORIAL
FORAGIAL
RAPTORIAL
SALTATORIAL
CURSORIAL
NATATORIAL

36. INSECT WINGS AND THEIR MODIFICATIONS
THORACIC APPENDAGES
INSECT WINGS AND THEIR MODIFICATIONS
Insects are the only flying invertebrates. Wings are present only in adult stage. Number of wings varies from two pairs to none.
There is only one pair of wings in the true flies. Normally two pairs of wings are present in insects and they are borne on pterothoracic segments viz., mesothorax and metathorax.
Venation (the arrangement of veins in the wings) is different for each group of insects and is used as a means of identification.

37. The wings of insects may have the following modifications –
Elytra
Halteres
Scales
Hemelytra
Frenulum
Hamuli
Tegmina

38. THE ABDOMEN AND ITS APPENDAGES
The abdomen is a highly flexible tagma formed by the fusion 9-11 segments
. Each abdominal segment is made up of only two sclerite namely dorsal body plate (tergum) and ventral body plate (sternum).
The first eight abdominal segments each bear a pair of spiracles. Abdominal appendages are genital organs and a pair of cerci at the tip of the abdomen. They cerci may be short, long or curved.
The abdomen is concerned with the function of reproduction and metabolism.

40. ADDITIONAL READING
Raven, P., Singer, S., Mason, K., Losos, J. and Johnson, G. (2013). Biology. 10th ed., McGraw-Hill Education, 1408 p.
Johnson, N. F. and Borror, D. J. (2005).
Borror and DeLong's Introduction to the Study of Insects. 7th ed., Thompson Brooks/Cole, 864p.
Chapman, R.F. (2013). Insect, structure and function.
Simpson, S.J and Douglas, A.E Eds., Cambridge University Press, New York,