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