Agricultural Entomology note

1. : Agriculture Entomology
(MSc.)

2. Chapter 1:
Forest Entomology

3. Entomology is the study of insect species and
their interaction in forest ecosystems.
its the study of forest insects, particularly those
insects which feed on or do damage to trees or
lumber.
Entomologists study insect biology, life cycles,
and classification, interactions with their host
plants and control/management strategies.
What is entomology ???

4. Entomology’ comes from the Greek word ‘
Entomos’- meaning insects
logy ---meaning study.
Entomology is the study of insects.
Insect is derived from Latin word “insectum”which
means “ cut in to”, which refers to segmented body
Entomologists study the development, anatomy,
physiology, life history, behavior, environment, and
classification of insects.
 The impact of insects on society is enormous.
What is Entomology???

5. Entomology classified as; Basic and applied entomology.
 Basic entomology is study of insect anatomy (body parts
and organs), Systematic (taxonomy and Phylogenetic),
physiology (growth & development) ecology
(interaction their environment of insects).
 Insect anatomy:- study of the external and internal
anatomy of insects
External anatomy is called morphology
Internal anatomy deals with the internal organs of
the insect body
 Physiology:- it is close association of the various
organs with essential chemical and physiological
processes.
Fields of Entomology

6.  Systematic entomology is consist of taxonomy
&Phylogenetic
 its study of the diversity of insects and their
inter-relationships
 Insect growth and development entomology
 is study of the developmental biology in insects
 Study of the cell biology, embryology,
morphology, physiology and molecular biology.
 It also defined as metamorphosis
 Insect ecology is study the interaction of insects
and their environment

7. Applied Entomology
Applied Entomology:- study of insect in the field which
consider as economic point of view
 The following are the important branches of
entomology:-
 Agricultural entomology
 Medical entomology
 Veterinary entomology
 Industrial entomology
 Forest entomology
 Forensic Entomology

8. Agricultural entomology- the study of insects, which are directly related with
the crops and the stored commodities.
Medical entomology- deals with the insects, which are responsible for
transmitting human diseases.
Veterinary entomology- the study of those insects, which may be beneficial
or harmful to the animals.
Industrial entomology- this is concerned with the insects, which are directly
or indirectly related with wood, wool, cloth and the other industrial
materials.
It also includes the study of beneficial insects like honey bee, lac
insect and silkworm.
Forest entomology- the study of insects concerning with forest plantation.
Forensic Entomology- Study and use of insects in crime investigations.

9.  Entomology are useful and harmful effects to humans, animals
and plant
Benefit of Entomology
Insect as pollinator–Insect pollinate crops and increases the
yield.
In sect serve as productive insects.
 Insects serve as food for birds, fish and other useful animals.
Insect serve as scavengers.
Insect as beneficial insects like Natural enemies.
increase soil fertility by decomposing dead plants and animals.
Weed feeders
Main objectives of study of Entomology

10.  Some insects are parasites of animals
 Parasites of plants by the construction of nests or
shelters.
 Vector of animal and plant diseases
 destroy crops and stored food
 destroy wooden structures
 spoil stored products and other materials
Harmful effects of Entomology

12. Characters of Arthropoda
 Segmented body
 Paired appendages
 Bilateral symmetry
 Chitinous exoskeleton
 Tubular alimentary system, with mouth & anus
 Open circulatory system
 Nervous system
 Respiration by gills, trachea, or spiracles
Chapter Two
Class of Insect in the Phylum Arthropoda
Relation of Insect with other Arthropods/characters of Arthropoda

13.  Arthropods are the most successful phylum based on
species diversity, distribution, and numbers of
individuals.
 Classes of Arthropods
Onychophora
Diplopoda
Chilpoda
Symphyla Group Assignment ?????
Crustacea
Arachinda
Insecta
This chapter concern on class of insecta
Classes of Arthropods

14. Class Crustaceans
Class Arachnids
Millipedes
Centipedes
sowbugs
Spiders,
ticks,
mites
scorpion
Crayfish
Class Onychophora
Class Symphyla
Class Diplopoda
Class Chilpoda

15. Onycophora
the common name of Velvet Worms or Walking
Worms
ancient animals
all terrestrial
only found in damp, moist habitats
normally nocturnal
have three pairs of modified legs making up their
head region
 The first of these are the two thick stubby antennae.

16. Diplopoda
Millipedes have two pairs of legs on all but the first three
body segments (47-375 leg pairs and 25-189 body segments,
not counting head and tail segment).
 Hatch with only 3 pair of legs, and gain more segments
and legs as they molt and grow
Millipedes lack the structures to bite, pinch, or sting, and
are harmless to humans, although the defensive secretions
burn if they get into the eyes.
The body of millipede is more cylindrical slow
moving and unable to bite

17. Chilpoda
Centipedes have only one pair of legs per body segment
 The last pair of legs extends backwards behind the body;
they can run fast and can bite.
Centipedes have a head bearing eyes, well developed mouthparts
and one pair of antennae.
The legs of the first body segment are modified into poisonous
jaws and are used for defense as well as for capturing prey.
Centipedes are insectivorous and often feed on other arthropods
as well.
The bodies of centipedes are flat

18. Some characteristics of class Chilopoda and Diplopoda.
They are essentially terrestrial
 Have clearly stated head.
 Other body segments are all similar.
 Contain 1 pair of antennae
 Contain 1 pair of mouth parts or jaws.
 The eyes may be plain, complex or not present.

19.  There are several identical legs, the pair in each
segment in Chilopoda and 2 pairs in every segment in
Diplopoda.
 There are no larval forms.
 The gaseous exchange is by trachea.
 Chilopodans are mostly carnivorous whereas
Diplopodans are mostly herbivorous.

20. Symphyla
Commonly called as garden centipedes or pseudo-
centipedes
 Looks similar to centipedes
Terrestrial soil dwelling arthropods
 Herbivorous detritus feeders
They are translucent, lack body pigmentation
Body is divided into head and trunk
The trunk consists of 15-22 segments with 10-12 pairs of
walking legs
 Juveniles have six pairs of legs

21. Crustacea
- Crayfish, sowbugs
-2 body segments and 5 pairs of legs
Arachnida
- Spiders, ticks, and mites
-2 body segments and 4 pairs of legs

22. Class of Insecta
Insecta means Hexapoda
Insects
 belong to Animal kingdom.
The phylum is arthropoda.
The term arthropod is derived from two Greek word
 arthros meaning ‘joint’ and
 poda meaning ‘leg’
Order belong to insecta (Hexapoda) meaning six legged
All arthropods have jointed legs and external skeleton
(Exoskeleton)

23. insects are the largest phylum of animal
kingdom
 In the animal kingdom, insects are covered
75% in the earth
They include animals differing widely in
structures but common on certain fundamental
characteristics.

24. Insects occupy 75% or 2/3rd of total population of
Phylum Arthropoda
What are the unique feature of insect?
Body is divided into head, thorax and abdomen
Head bears a pair of antennae,
Three pairs of legs bears in thorax region
 one or two pairs of wings in the adult stage
Example- Insects (like house flies, grasshoppers, etc.)

25. Why study insects?
Insects are the dominant group of organisms on earth,
in terms of both taxonomic diversity and ecological
function!

Can you count the ant’s legs?

26. Distinguishing characteristics of insects
Bilaterally symmetrical animals
 Metameric segmentation i.e., body of the animal is divided into
a succession
Body is divided into three regions namely Head + Thorax +
Abdomen(11-12 segments).
Majority of the segments posses pair of jointed appendages
Exoskeleton contains chitin secreted by epidermis
Specialized alimentary canal with chitinous teeth
 Metamorphosis takes place in the development
No animals exhibit the above combinations of characters.

27. All insects have:

28. Insects and their relation to humans
 Some insects are useful to humans, and harmful to humans
 But some others are more or less indifferent to human
beings and their surrounding
Benefit of insects to humans
Pollinators flowers
 Some crops depend upon insects for pollination and
fruit setting
 Aid in the production of fruits, seeds, vegetables, and
flowers
 Improve soil fertility
 Some insects increase soil fertility by decomposing
dead plants and animals. e.g. dung beetle, termites, etc.
 Improve physical condition of soil and promote
fertility by burrowing.

29.  Weed feeders
 Some insects are feeder of weeds which consider
as herbicides
 Entomophagous insects/Parasites
Many insects destroy other injurious (pest) insects that
attack cultivated crops
Live on or in the bodies of living organisms (hosts)
Host are usually larger and stronger than the parasites
and are not killed
 Example: Dragon fly, Preying mantid, Lady bird
beetles, Robber flies and Parasitic wasps of aphids

30. Scavengers
Its consuming bodies of dead animals and plants
 Bury carcasses and dung
 Ex. Termites, ants and other wood feeding insects
help in the conversion of fallen trees and logs to
soil
 Dung beetles hasten the decomposition of dung
 Predators
 Catch and feed on other creatures (prey)
 Ground beetles
 Lace wings and lady bugs
 Insects producing commercial products
The larvae of Bombyx mori (silk worm) produce
commercial silk fibers.
 The honey bees produce honey as well as bee wax.

31. The bee wax is used in the manufacture of
ink, carbon paper, electrical insulators,
sewing threads, and polishes for floor, furniture,
shoe and leather.
Cosmetics which are produced from bees wax
include creams, lotions, lipsticks, etc.
Bee venom is used in the production of
medicines against diseases such as paralysis and
rheumatic disease.

32. Insects served as food
 Some insects serve as food for many animals like-
humans, birds, chickens, etc.
Insects act as food for fishes, bird's chickens etc.
In many parts of the world, from ancient times to
present day insects have been eaten extensively by
human beings
 The Arabs eaten by locust
 In certain parts of Africa: ants, termites, beetle grubs,
caterpillars and grasshoppers are eaten.

33.  Useful for Research
 Insects are subjects of research
 Aesthetic and Entertaining value of insects
 Insects like butterflies serve as models for
artists, florists, decorators
 Insects with cryptic coloration (Jewel beetles)
are used as ornamentals
 Some insects sing songs that are interesting

34.  Insects in medicine and surgery
 Blow fly larvae are used in treating decaying
tissues (Severe wounds)
 Entomologists are kill or at least control insects but
entomology includes the study of many positive aspects
of insects.
Entomologists reported that less than 3 % from all
insects are harmful to humans while others are useful or
neutral groups.

35. Benefit of insect

37. Harmful effects of insects
 Detrimental Effects of Insects
 Some insects are parasites of animals
 e.g. Horse fly, Stable fly, Cattle fly
 Parasites of plants by the construction of nests or
shelters.
 Vector of animal and plant diseases
 Some insects destroy crops and stored food
 Some insects destroy wooden structures
 e.g Termites

38.  Insects as parasites of animals.
 E.g. blood sucking fleas, bed bugs, lice, etc.
 Insects as carriers of animal diseases
 E.g.- mosquitoes cause malaria and
- Tsetse fly (Glossing spp)
- Trypanosomiasis in cattle's.
Insects spoil stored products and other materials
 Some insects act as house hold pests:
 e.g. Ants, Termites, Silver fish, Cockroach, Crickets,
Cloth moths

39. Harmful insect

41. Measures of dominance
1. More number of species
In the animal kingdom more than 85 per cent of the species belongs
to insect group.
2. Large number of individuals in a single species:
e.g., Locust swarm comprising of 109 number of individuals,
occupying large area.
3. Great variety of habitats:
 Insects thrive well under varied conditions.
 ¾ Insects are distributed every where from cooler parts to hottest
tropics.
 They live in water, land, air, deserts, high mountains etc.
4. Long geological history:
 Insects were known to occupy this earth for more than 350 million
years, which is a good track record.
 This has given the insects great variety of adoptions under different
conditions.
Chapter: Three
Dominance of Insects

42. How many different species of insect are
there?

43. The richness of insects:
LEPIDOPTERA
175,000
ORTHOPTERA
20,000
6/17/2022 9:22 AM 43
Debre Berhan University SGS Plant
Protection

44. Adaptive features for the success of insects
Exoskeleton
Small size
Flight
Hexapod locomotion
 Compound eyes
High fecundity
Method of reproduction
Short life cycle
Wide adaptability
Dormancy
Zenith of evolution

45. Exoskeleton:
Insect body is covered with an outer cuticle called
exoskeleton which is made up of a cuticular protein
called Chitin.
It helps to gives strength, rigidity and flexibility to
the insect body.
Its provides for muscle attachment
Its hard area to protects the internal organs from
mechanical injury
It prevents desiccation (Water loss) from the body

46. Small size: It helps to:
 Less space for shelter
 Less food, and energy requirements for
development and sustaining life.
 Energy Utilization maximum.
 Less gravitational effect-its help to fly
 Muscular action and tracheal respiration
more effective.
 Easy escape from enemies.

47.  Flight
 Insects have functional wings
 Insects are the only invertebrates that can fly.
 Flight is used for the following purpose.
 To seek food, mate, shelter and oviposition sites
 To colonize in a new habitat and also to exchange
habitat.
 To escape from enemies and unfavorable
conditions.
 To migrate (i.e. for long distance travel e.g.
Locusts)
 to expand more quickly into new habitats and
exploit new resources.

48. Hexapod locomotion: the presence of three pair legs
on the three thoracic segments, which are important for
locomotion.
Compound eyes: Most of the adult insects and
nymphs consists of compound eyes as visual organs
which possess number of hexagonal units known as
ommatidia.
Because of presence of number of ommatidia which
enhance the power of vision

49. High Reproductive potential
Reproductive potential of insect is high due to the following
reasons:
High fecundity:
 Fecundity is defined as the egg laying capacity of female
insects.
 It helps to increase the population at faster rate
 they produce 100-150 even more than eggs per female.
 e.g., Queen termite lays 6000 - 7000 eggs per day for 15 long years.
 This enable insects dominates the ecosystem.

50. Development period is short
 one generation is completed within a short period of 16 days,
which favors greater genetic changes in the insect population,
like quicker development of insecticide resistant strains
e.g., Corn aphid produces 16 nymphs per female which reaches
the adulthood within 16 days
 Short life cycle:
 Most of insects have very short life cycle i.e. 2 to 4 weeks which
help insects to complete more number of generations in a definite
period of time

51. Method of reproduction: Insects can reproduce both sexually
as well as parthenogenitically.
Presence of special types reproduction
 Polyembryony: Development of many individuals from a
single egg.
 e.g. parasitic wasps.
 Parthenogenesis: Reproduction without male or without
fertilization,
 e.g. aphids
 Paedogenesis: Reproduction by immature stages.
 e.g. certain flies.

52. Wide adaptability
Adapting quickly in the face of a changing environment.
(high reproductive potential, short life cycles, large and diverse populations)
continually change as new resources appear and old ones
disappear
Some insects occur on mountains peaks
high 6000 meter
 Others live in arctic temperature
 below -20oc.
 tolerate temperatures -48 to 52oc.
 They are also well adapted to dry & hot (xerophytic) conditions
of deserts
Pests developed resistance to chemical and biological insecticides
Dormancy
Some insects’ species have arrested development
Occur environmental conditions are unsuitable
such as
 seasonal extremes of high or low temperatures
drought.

53. insects have vast diversity of food habits. I.e. they may be monophagous /
oligophagous/ polyphagous insects
Scattered sense organs: The sense organs viz., visual organs, gustatory
organs, organs of touch etc.
 distributed on different parts of the body such as antennae, eyes, mouth
parts in the head, legs with claws on thorax, cerci in the abdomen etc.
 This scatteredness on all parts of the body prevents the chance of all
being damaged
Zenith of evolution:
It is observed in social insects
Division of labor is seen
They have developed their own dance languages to locate the food
sources