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Internal Insect
Morphology
Circulation System
Organization:
Humans – closed
Our circulatory system consists of a
heart and a series of tubes (arteries
and veins) intimately associated with
every cell
Insects – open
Blood Cavity
(Hemocoel)
Entire open area (here in white) is a
blood filled cavity called the Hemocoel.
The insect circulatory system:
Hearts and Ostia - Ostia are one-way valves that
allow blood to enter heart. It is then forced out via
the aorta.
Aorta
The 9 hearts
Hearts
Aorta
Generalized circulation path
of blood in insects.
Not a very efficient system and would not
work for humans but is effective for insects
because of the limited functions of
circulatory system
Circulatory system functions:
•Transport - food
•Protection – immune system
•Hydraulic – inflates wings
•Respiration (minor)
•Thermoregulation – cools/warms
Blood characteristics:
1) Color
2) Contents
Sodium, Potassium, Calcium,
Magnesium & other salts, water
Digestive System
Consists of 3 regions:
1) Foregut 2) Midgut
3) Hindgut
Salivary Glands: Function as a food solvent,
digestive enzymes, produce glue, silk, plant
hormones (IAA).
Foregut (exoskeletal): esophogus
Conducts, stores, guides foods
Midgut (mesodermal): small intestine
Major site of food absorption
Enzyme production
Hindgut (exoskeletal): large intestine
Transports waste from body
Reabsorbs water and eliminates Uric acid
Digestive Process
•Intestinal: normal digestive process
•Extra-intestinal: Digestion outside the
body by regurgitation of enzymes onto
or into food before ingestion
•Microbial aids – termites and bacteria
necessary to digest cellulose
Adaptations to a Liquid Diet
Aphids and Scale Insects Produce “Honey dew”
First Stomach with
filter chamber
Second Stomach enzymes added here
Rectum - Excess water
and some sugars leave
body
Excretory System:
Hindgut maintains internal environment suitable
for survival of the insect
It does this by:
1) Eliminating nitrogenous waste from the blood
2) Regulating salt and water and Uric Acid (H20)
Structures: Malpighian tubules / insect kidneys
Foregut
Midgut
Hindgut
Malpighian tubules
Ventilation: Respiration
Tracheal System: a system of air tubes
that carry gases to and from body
tissues.
Trachael
system of
an insect.
There are three parts to the Tracheal System:
1) Spiracles: external openings of the tubes
2) Tracheae
3) Taenida: spiral bands of the exoskeleton
in the wall of trachea – add strength
Mode of action:
Diffusion
Pumps
Efficiency – diffusion works well for insects
because they are small
Spiracles
Tomato Horn Worm
Taenidia are spiral bands of the
exoskeleton in the wall of trachea.
Nervous System Brain - Ventral Nerve Cord - Ganglia
and axons throughout body
Brain
Subesophageal
Ganglion
Thoracic Ganglia
Ventral Nerve Cord
Ganglia and axons of the insect body.
Brain
Role:
•Receive and integrate sensory data
•Little coordination like in humans
•Other functions - walking, flying,
mating are under control of nearby
ganglia
What happens if you cut off
the head of an insect?
Metamorphosis Nightclubs
Insect Growth and Development
•Exoskeleton limits growth
•Shedding exoskeleton (ecdysis) - necessary to
grow and/or change shape
•Ecdysis involves loss of: Outside body
covering, the foregut, the hindgut and tracheal
system
•Instars - the insect between molts
This much area is “digested” and
recycled into new exoskeleton.
Cicada nymph casing – very thin and brittle
Metamorphosis – Change in shape or
form
Regulated by 3 hormones:
•Ecdysone - molting hormone
•Juvenile Hormone
•Brain Hormone
Types of Metamorphosis:
1)Simple metamorphosis Juvenile (young)
insects look much like what they will look like as adults-silverfish, bristletails
Types of Metamorphosis:
2)Incomplete --
Ephemeroptera –
Mayflies
Eggs
Nymph
Naiads
Adults
Hemiptera – True bugs
Gradual Metamorphosis
Types of Metamorphosis:
4) Complete – Lepidoptera, Coleoptera, Diptera,
Hymenoptera, Thysanoptera
Eggs
Larva
Pupa
Adult
End of
Basic Entomology
Part II