introduction to entomology

1. Introduction to Entomology

2. What is Entomology?
- the branch of zoology
that deals with the study
of insects.
- who study insects are
known as Entomologists.

3. NUMBER AND BIODIVERSITY OF INSECTS
the largest, most successful and
most diverse form on the planet.
more widely distributed over the
earth than any other animal phylum
live in virtually every habitat on
earth
research on various insects species
reveals that there are about 5 million
species of insects.
They account for around 75% of
total animal species on earth.
Every year thousands of new species
has been discovered.

4. INSECT DIVERSITY
25-27% 10-13%
60-65%
Long term survival
400 m yrs in Devonian Pd while man is 2-3 m yrs old
during Pleistocene Pd.
Abundance
More no. of species
Varied habitats
All kind of habitats, from aquatic to desert, cold to hot

5. Following are some of the reason for cosmopolitan
distribution of insects:
1.Many human-loving (anthropophilic) insects eg.
Houseflies, cockroaches and silverfish accompany
humans everywhere.
2.Many human associated (synanthropic) insects
bedbugs, ticks & lice act as ecto or endoparasites on
humans and get distributed to different places.
3.Phytophagous (plant feeding) insects are spread
where plants are present.
4.Some insects spread due to anthropogeny (aided by
humans) for use as biological control. Eg- Coccinella
(lady bird beetles) is used to control mustard pests
(aphids).
5.Coprophages (dung feeding) insects eg. Dung
beetles

6. WHY INSECTS ARE SO SUCCESSFUL ?
Insects are the only animals giving
challenge to man for his supremacy.
 They occupy more than 2/3 of the known
species of animals. They have been upon
earth for 400 million years.
Insects have great potential for rapid
rise in population through a variety of
ways.
Insects are the most successful forms of
life on this planet. They are typically very
small.
They locomote in a variety of ways,
including swimming, jumping, gliding, flying,
skating, clinging, floating, crawling, walking,
running, and/or drifting.

7. The insects do have a unique
combination of characteristics which, as
a whole, have given them an unusual
survival advantage. In brief, these
attributes include an
1. Exoskeleton: an insect's supporting
skeleton is located on the outside of its
body. This exoskeleton is a marvelous
structure that not only gives shape and
support to the body's soft tissues, but
also provides protection from attack or
injury, minimizes the loss of body
fluids in both arid and freshwater
environments, and assures mechanical
advantage to muscles for strength. As
a "suit of armor", the exoskeleton can
resist both physical and chemical attack.

8. 2. Small body size: Another
advantage of small size is the
minimal resources needed for
survival.
A crumb is a feast; a dewdrop
quenches thirst; a pebble provides
shade.
In some cases, food requirements
are so modest that an insect may
live on a single plant or animal for
its entire life and never exhaust its
food supply.

9. Finally, small size is a big advantage to
insects that must avoid predation.
They can hide in the cracks of a rock,
beneath the bark of a tree, behind the
petal of a flower, or under a blade of
grass.
Dichomorpha echmepterygis is the
world’s smallest insect. Discovered in
1997, this Costa Rican wasp (family
Mymaridae) is a parasite of other
insects' egg. Adult males may be only
0.139 mm (0.00055 inch) in length --
nearly 1/3 smaller than some single-
celled protozoa (e.g., Paramecium
caudatum).

10. 3. The ability to fly: Flight gave these insects a
highly effective mode of escape from
predators that roamed the prehistoric
landscape. It was also an efficient means of
transportation, allowing populations to
expand more quickly into new habitats and
exploit new resources.
4. High reproductive potential: In insect
populations, females often produce large
number of eggs (high fecundity), most of the
eggs hatch (high fertility), and the life cycle
is relatively short (often as little as 2-4
weeks). Together, these three characteristics
enable insects to produce remarkably large
numbers of offspring. A typical female lays
100-500 eggs in her lifetime, but numbers in
the thousands are not uncommon.

11. American dog tick female laying egg mass (1000-2000 eggs!).

12. 5. Metamorphosis: Most insects undergo
significant developmental changes as they
grow from immature to adults. These
changes, collectively known as
metamorphosis, may involve physical,
biochemical, and/or behavioral alterations
that promote survival, dispersal, and
reproduction of the species.
Types: Incomplete & complete
metamorphosis
– In some insects the transformation
process is slow and does not include all body
tissues (incomplete metamorphosis) the
immature and adults share many
characteristics -- they often live in similar
habitats and feed on similar types of food.

13. Incomplete
INCOMPLETE
METAMORPHOUS
Insects change
shape gradually!

14. Incomplete meta
Incomplete Metamorphosis
egg naiads adult
This life cycle starts as an egg, but each growth, or
nymphal stage looks similar, except it lacks wings and the
reproductive capacity that the adult possesses. The
"incomplete" metamorphosis which is found among the
aquatic insect orders such as mayflies (Ephemeroptera)
and dragonflies (Odonata).

16. Complete Metamorphosis
• Egg -Larvae-Pupae-Adult
Larvae not look like adult- are wormlike
Can live in different environment
Eat different food
Larvae usually the main pest
Lepidoptera (butterflies)
&
Hymenoptera (bees, ants, wasps)

17. Complete
Metamorphosis
Four stages that
all look different

18. Complete Metamorphosis

19. 6. Adaptability in an ever-changing environment:
they were among the first creatures to invade the
dry land and exploit green plants as a source of food,
they were the first animals to use flight as an escape
from predators. As a group, they have endured 400
million years of climatological and geophysical
upheaval, including the evaporation of inland seas,
formation of mountain ranges, shifts in continental
plates, onset of ice ages, and the fallout from cosmic
impacts.

20. Just within the few thousand years since humans
began roaming the earth, insects have acquired a
taste for new products that would never be a part
of their "natural" environment: e.g., glue and
wallpaper paste, book bindings, cardboard,
paintbrushes, tanned leather products, the corks of
wine bottles, mummies, stuffed museum
specimens, chocolate, ginger, yeast cakes,
tobacco, pepper, and even potent drugs like
marijuana and opium.

21. Perhaps the most remarkable example of insect
adaptation in this century has been the speed with
which pest populations have developed resistance to a
broad range of chemical and biological insecticides.
After World War II, public health officials in the United
States made a concerted effort to eradicate the house fly
(Musca domestica) with DDT.
For several years the campaign seemed promising: fly
populations decreased. But a few resistant flies
managed to survive because they were endowed
with an enzyme that could detoxify DDT. These
survivors reproduced and passed this resistant trait to
their offspring. In time, DDT-resistant flies repopulated
their environment and the species now appears to be
living happily ever after!

22. Insects affect man’s interest in many ways:
-Because they dominate all terrestrial
environments that support human life,
insects are usually our most important
competitors for food, fiber, and other
natural resources.
-Some insects act as vectors of some
diseases and some also attack wood
workings, stationary articles and
museum specimens.

23. • Some other insects affects man’s
health. Mosquitoes, housefly and rat
flea are some insects transmit diseases
to man. For E.g. Bubonic Plague
epidemic that wiped out the population
of Europe in the 14 century was carried
by fleas that infested rodents.
• However, many insects are harmless
and beneficial to human beings. They
are productive insects like honey bees,
silk worm and lac insects.
• Ecological impact: insects can acts as
scavengers (aerate the soil by nest and
burrows) and decomposers (enhancing
decomposition of manure (beetles).