Insects and relatives
Valentina Cipriani
Natalie Sarracino
What are insects?




Insects are classified within arthropods (segmented
body) that have an exoskeleton that mostly consists of
chitin, a three part body (includes head, thorax, and
abdomen), three pairs of jointed legs, and 2 antennae .
Chitin: complex carbohydrate that makes up the cell
walls of fungi and is also found in the external skeleton
of arthropods.
They are among the most diverse group of animals on
the planet and include more than a million described
species.
Represent more than half of all known living organisms.
Digestion




The digestive system of an insect is used to extract
nutrients and other substances from the food it
consumes.
Most of this food is ingested in the form of
macromolecules and other complex substances like
proteins, polysaccharides, fats, and nucleic acids.
Macromolecules: a very large molecule commonly
created by some form of polymerization.
The macromolecules are then broken down into smaller
molecules like amino acids and simple sugars before
being used by cells of the body for energy, growth, or
reproduction.
Respiration



Insects conduct respiration without the use of
lungs.
Instead, they use a respiratory system that
consists of internal tubes and sacs through which
gases either diffuse or are actively pumped which
deliver oxygen directly to tissues that need it.
Since oxygen is delivered directly, the circulatory
system is not used to carry oxygen, and is
therefore greatly reduced.
Gas exchange




Gas exchange patterns in insects can range from
continuous and diffusive ventilation, to discontinuous gas
exchange.
During continuous gas exchange, oxygen is taken in and
carbon dioxide is released in a continuous cycle.
Diffusive ventilation is simply a form of continuous gas
exchange that occurs by diffusion rather than physically
taking in the oxygen.
In discontinuous gas exchange, however, the insect
takes in oxygen while it is active and small amounts of
carbon dioxide are released when the insect is at rest.
Reproduction



The majority of insects hatch from eggs.
The fertilization and development takes place
inside the egg, enclosed by a shell.
Some insects use parthenogenesis, a
process in which the female can reproduce
and give birth without having the eggs
fertilized by a male.
Metamorphosis




Metamorphosis in insects is the biological process of
development that all insects must go through.
The two types are : incomplete metamorphosis and
complete metamorphosis.
Incomplete metamorphosis: The insects change
gradually by undergoing a series of molts. An insect
molts when it outgrows its exoskeleton.
Complete metamorphosis: where the insect changes all
in four stages, an egg or embryo, a larva, a pupa, and
the adult or imago.
Relation to humans



Many insects are considered pests by humans. Insects commonly
regarded as pests include those that are parasitic (mosquitoes, lice,
bed bugs), transmit diseases (ex. malaria ), damage structures
(termites), or destroy agricultural goods.
Despite the amount of effort focused at controlling insects, human
attempts to kill pests with insecticides can backfire. If not used in the
proper way.
The poison can kill all kinds of organisms in the area, including
insects' natural predators such as birds, mice, and other
insectivores.
Insect relatives




Insects, centipedes, and millipedes are all in the phylum
Arthropoda and are classified as uniramians.
Uniramians have jaws, one pair of antennae, and
unbranched appendages or body parts.
Although insects and their relatives share these
characteristics as uniramians their different forms and
lifestyles separates them into different categories.
Centipedes and millipedes are classified into a separate
sub phylum called myriapods meaning many legs. Their
different characteristics separate them from insects.
Contrasting the Two
Insects
Centipedes and Millipedes (Relatives)
Compact Bodies
Long Bodies
Three part bodies
Wormlike
Are adapted for flight
Do not fly. Stay close to the ground
Have 3 pairs of legs
From 100-1000 legs
Go through metamorphosis
Don’t go through metamorphosis
Centipedes






Contain from a few to more than 100 pairs of legs.
Most body segments contain one pair of legs each.
Centipedes are carnivorous. Their mouths include
venomous claws which they use to catch, stun, or kill
their prey usually during nighttime.
Usually live under rocks or in the soil.
Do not contain a waterproof coating on their
exoskeleton.
Because of this their bodies loose water easily and they
must live in moist or humid areas.
Millipedes






Highly segmented body.
Each segment contains two instead of one pair of legs
each which result from the fusion of two segments in the
millipede embryo.
Live under rocks and decaying logs.
Millipedes are herbivores and feed on dead and
decaying plant material.
Are fearful, gentle creatures who roll themselves up into
a ball to protect themselves when they are bothered.
Also defend themselves by secreting unpleasant or toxic
chemicals.
Centipedes and Millipedes
Cont’
Cylindrical
More
flattened
Long Hind Legs
Reproduction
Centipedes


Male deposits sperm
bundles leaving the female
to find them.
Some females species
abandon their eggs, leaving
the newly born centipedes
to manage on their own yet
some nurture their offspring
until they are ready to
handle things by
themselves.


Millipedes
Male and female join in
mating.
All female species remain
with their eggs until they
hatch and nurture their
offspring until they are no
longer dependent on them.
Both
Lay their eggs in underground nests.
Life Cycle







Spend the winter as adults in a protected habitat and become
active in the spring.
During the warmer months, females lay eggs in soil and cover it
with a sticky substance to keep them together in clumps of
between 10 and 60 eggs. Some species do give birth to living
offspring though.
They then undergo the Immature stage (larvae), when the
centipede or millipede hatches from the egg and looks similar to
an adult only smaller with fewer leg bearing body segments.
Develop through several molts and stages in which more and
more leg bearing segments are produced.
Some centipedes go through anamorphy in which each molt
adds legs to the body during the larvae stage. Other centipedes
go through epimorphy in which they hatch with a full set of 15
pairs of legs.
Millipedes develop through about 7 stages in 21 to 25 weeks.
Some centipedes can live up to 6 years.
The End
