Internal Insect Morphology

Circulation System

Organization:Humans – closedOur 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.

AortaThe 9 hearts

Generalized circulation path of blood in insects.

Hearts Aorta

Circulatory system functions:

•Transport - food•Protection – immune system•Hydraulic – inflates wings•Respiration (minor) •Thermoregulation – cools/warms

Not a very efficient system and would not work for humans but is effective for insects because of the limited functions of the circulatory system

Blood characteristics:1) Color

2) ContentsSodium, Potassium, Calcium, Magnesium & other salts, water

Digestive System

Consists of 3 regions:

1) Foregut 2) Midgut 3) Hindgut

Foregut : esophogusConducts, stores, guides foods

Midgut : small intestine Major site of food absorption Enzyme production

Hindgut : large intestineTransports waste from bodyReabsorbs water and eliminates Uric acid

Salivary Glands: Function as a food solvent, digestive enzymes, produce glue, silk, plant hormones (IAA).

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 withfilter chamber

Second Stomach -enzymes added here

Rectum - Excess waterand some sugars leavebody

Excretory System:

Maintains internal environment suitable for survival of the insect

It does this through two structures/processes:1) Malpighian tubules = Eliminates nitrogenous

waste from the blood

2) Hindgut = Regulates salt and water and Uric Acid (H20)

Ventilation: Respiration

Tracheal System: a system of air tubesthat carry gases to and from bodytissues.

Trachael system of an insect.

There are three parts to the Tracheal System:

1) Spiracles: external openings of the tubes 2) Tracheae: transport air through body3) Taenida: spiral bands of the exoskeleton

in the wall of trachea – add strength

Mode of action:

DiffusionPumps

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.

Thoracic Ganglia

Brain

SubesophagealGanglion Ventral Nerve Cord

Nervous System Brain - Ventral Nerve Cord - Ganglia and axons throughout body

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 nearbyganglia

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

This much area is “digested” andrecycled into new exoskeleton.

Cicada nymph casing – very thin and brittle

•Instars - the insect between molts

•Generations – egg to adult. How many per year? > 2 per year = pest

Metamorphosis – Change in shape or form

Regulated by 3 hormones:

•Ecdysone - molting hormone

•Juvenile Hormone

•Brain Hormone (PTTH) = prothoracicotrophic 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 –

MayfliesEggs

NymphNaiadsAdults

Hemiptera – True bugsGradual Metamorphosis

Types of Metamorphosis:4) Complete – Lepidoptera, Coleoptera, Diptera,Hymenoptera

EggsLarvaPupaAdult

Reasons for Insect Success

• Flight

• Complete Metamorphosis

• Elytra Wing Cover

End of Basic EntomologyPart II