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
Generalized circulation path of blood in insects. HeartsAorta
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 circulatory system
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 (H 2 0) Structures: Malpighian tubules / insect kidneys
ForegutMidgutHindgut 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.
Thoracic Ganglia Brain Subesophageal Ganglion 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 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