Entomology -- Week 9b

To deliver oxygen directly to tissues through a network of air-filled tubes (tracheae), bypassing the circulatory system.

What is the purpose of the tracheal system in insects?

What are spiracles and what is their role?

external openings along the thorax and abdomen that allow air to enter the tracheal system.

Through diffusion and sometimes active ventilation; oxygen enters via spiracles, diffuses through tracheae to tissues, and CO₂ exits the same way

How do terrestrial insects exchange gases?

1. Gills (e.g., mayfly nymphs)

2. Plastrons (air-retaining structures)

3. Breathing tubes (e.g., mosquito larvae)

4. Cutaneous respiration (gas exchange through thin exoskeleton)

5. Air bubbles (carried from surface for temporary oxygen supply)

Name five adaptations for gas exchange in aquatic insects.

An open circulatory system, where hemolymph flows freely through body cavities rather than confined to blood vessels.

What type of circulatory system do insects have?

It transports nutrients, hormones, and waste—not oxygen—and plays a role in immune defense and thermoregulation.

What is the purpose of hemolymph in insects?

Ingestion and mechanical breakdown of food; includes structures like the esophagus and crop.

What is the role of the foregut in insect digestion?

Site of enzymatic digestion and nutrient absorption.

What is the function of the midgut in insects?

Reabsorbs water and salts; compacts waste into feces for excretion.

What does the hindgut do in insects?

Excretory organs that remove nitrogenous waste from hemolymph and regulate water and ion balance.

What are Malpighian tubules?

How do microbial mutualisms assist in nitrogen fixation for insects?

Symbiotic microbes in the gut or specialized structures convert nitrogen into usable forms, aiding insects with nitrogen-poor diets (e.g., termites).

Skeletal muscles

Attach to exoskeleton, control movement.

Visceral muscles

Surround internal organs, control gut and reproductive systems.

Muscles that contract once per nerve impulse; used for slower, more controlled movements (e.g., walking, low-frequency wingbeats).

What are synchronous muscles in insects?

Muscles that contract multiple times per nerve impulse; allow for rapid, high-frequency actions like fast wingbeats in flies or bees.

What are asynchronous muscles in insects?

In high-speed, energy-efficient movements like sustained flight at high wingbeat frequencies.

When are asynchronous muscles more useful than synchronous ones?