Entomology Exam 2

Open circulatory system

Hemolymph leaves vessels and flows through the hemocoel, bathing organs directly

Dorsal vessel

Tube along the insect’s back that pumps hemolymph; its posterior portion functions as a heart

Ostia

Openings through which hemolymph enters the dorsal vessel

Hemocoel

Body cavity through which hemolymph circulates

Path of hemolymph

Hemocoel → ostia → dorsal vessel → anterior discharge → hemocoel

Spiracles

External openings that admit air into the tracheal system

Tracheae

Air-carrying tubes that branch throughout the insect body

Taenidia

Spiral reinforcements that help keep tracheae from collapsing

Tracheoles

Fine tracheal branches where gases diffuse between the air and tissues

Air sacs

Expandable parts of the tracheal system that can help move or store air

Path of oxygen to a tissue cell

Atmosphere → spiracle → trachea → tracheole → tissue cell

Diffusion

Passive movement of gases from higher to lower concentration

Active ventilation

Body movements that increase airflow through the tracheal system

Do insect tissues usually receive oxygen from hemolymph?

No; the tracheal system generally delivers oxygen directly to tissues

How do respiration and circulation support flight?

Tracheae supply oxygen to flight muscles, while hemolymph transports nutrients and helps distribute heat

Foregut (stomodaeum)

Ingests, transports, stores, and sometimes mechanically processes food

Crop

Foregut chamber that stores food before digestion

Proventriculus

Foregut structure that can grind or regulate the passage of food

Midgut (mesenteron)

Main site of digestion and nutrient absorption

Microvilli

Tiny projections that increase the absorptive surface area of midgut cells

Peritrophic matrix

Protective, permeable lining around food in the midgut of many insects

Hindgut (proctodaeum)

Reabsorbs water and ions and forms feces

Malpighian tubules

Excretory structures that transfer wastes and ions from hemolymph into the gut

Rectal pads

Hindgut structures that recover water and ions

Uric acid

Nitrogenous waste that can be eliminated with relatively little water

Fecal elimination

Removal of undigested material and wastes through the anus

Active excretion

Energy-dependent movement of substances into excretory fluid

Path of food through the gut

Foregut → midgut → hindgut → anus

Path of nitrogenous waste

Hemolymph → Malpighian tubules → hindgut → anus

Main challenge for blood feeders

Rapidly eliminate excess water, regulate ions, detoxify heme, and excrete nitrogenous wastes

Main challenge for sap feeders

Eliminate excess water and sugars while obtaining scarce essential amino acids

Main challenge for dry-food feeders

Minimize water loss and recover water and ions from the hindgut

Main challenge for wood feeders

Digest resistant, nitrogen-poor tissue, often with help from microbial symbionts

Main challenge for leaf feeders

Process bulky tissue and detoxify, tolerate, or eliminate plant defensive compounds

Main challenge for pollen feeders

Release amino acids, lipids, sterols, and other nutrients from resistant pollen grains

Central nervous system (CNS)

Brain and ventral nerve cord, including ganglia, that process information and coordinate responses

Brain

Anterior CNS region involved in sensory processing and behavioral control

Ventral nerve cord

Nerve pathway linking the brain with ganglia elsewhere in the body

Segmental ganglia

Clusters of neurons that process information and coordinate activity in body segments

Peripheral nervous system (PNS)

Nerves outside the CNS that connect it to receptors, muscles, and organs

Somatic PNS

Peripheral pathways associated with sensory input and body movement

Visceral PNS

Peripheral pathways associated with internal organs and their regulation

Sensory neuron

Carries information from a receptor toward the CNS

Motor neuron

Carries commands from the CNS toward an effector, such as a muscle

Connectome

Map of connections among neurons in a nervous system

Chemoreceptor

Receptor that detects chemical stimuli

Olfactory receptor

Chemoreceptor that detects airborne chemicals, such as odors

Gustatory receptor

Chemoreceptor that detects chemicals through contact, such as sugars on a flower

Mechanoreceptor

Receptor that detects physical forces, movement, or touch

Proprioceptor

Receptor that detects the position or movement of body parts

Photoreceptor

Receptor that detects light

Thermoreceptor

Receptor that detects temperature

Hygroreceptor

Receptor that detects humidity

Compound eye

Eye made of many visual units called ommatidia

Ommatidium

Individual visual unit of a compound eye

Ocellus

Simple eye that primarily detects light intensity

Apposition eye

Compound eye in which each ommatidium receives light relatively independently; suited to brighter conditions

Superposition eye

Compound eye that combines light from multiple facets to improve sensitivity in dim conditions

Tympanal organ

Hearing organ that detects sound through vibrations of a membrane

Tympanal membrane

Thin membrane that vibrates in response to sound

Tympanal chordotonal organ

Sensory structure that detects vibration of the tympanal membrane

Tymbal

Sound-producing membrane that rapidly buckles and rebounds

General stimulus-to-behavior pathway

Stimulus → receptor → sensory neuron → CNS processing → motor neuron → effector → behavior

How might an insect respond to floral odor?

Olfactory receptor detects odor → sensory signal reaches CNS → motor output directs movement toward the flower

How might an insect respond to bat ultrasound?

Tympanal organ detects sound → CNS processes the signal → motor output triggers evasive behavior

Wing blade

Broad wing surface that interacts with air to generate aerodynamic forces

Wing veins

Structures that support the wing and carry nerves and hemolymph

Wing hinge

Joint that connects the wing to the thorax and allows wing movement

Tegmen

Leathery forewing that offers protection while retaining some flexibility

Elytron

Hardened beetle forewing that protects the hindwing and body

Hemelytron

Forewing with a hardened basal region and membranous tip, characteristic of many true bugs

Halteres

Modified wings that sense body rotation and aid flight stability

Wing loading

Body weight relative to wing area; higher loading generally requires faster flight to remain aloft

Wing aspect ratio

Wing length relative to width; long, narrow wings generally have higher aspect ratios

Broad, rounded wings

Often favor maneuverability and lift at low speeds

Long, narrow wings

Often favor efficient sustained flight, but may reduce maneuverability

Maneuverability versus endurance

Wing designs that aid sharp turns may be less efficient for prolonged travel

Protective versus aerodynamic forewings

Hardened forewings protect the body but can add weight or limit aerodynamic performance

Dispersal versus resident morphology

Dispersal forms invest in flight capability; resident forms may invest more in reproduction

Imaginal discs

Larval tissues that develop into adult structures, including wings, during complete metamorphosis

Wing pads

External developing wings seen in immature insects with incomplete metamorphosis

Non-flight functions of wings

Can include protection, communication, display, and thermoregulation

Reproduction and sex determination
Ovarioles

Egg-producing units of the ovaries

Testes

Organs that produce sperm

Spermatheca

Organ in which a female stores sperm after mating

Parthenogenesis

Development of offspring from unfertilized eggs

Arrhenotoky

Parthenogenesis that produces males

Thelytoky

Parthenogenesis that produces females

Deuterotoky

Parthenogenesis that produces both males and females

Heterogony

Alternation between sexual and asexual generations

XX/XY sex determination

System in which females are typically XX and males XY

XX/XO sex determination

System in which females are typically XX and males have one X chromosome

ZW/ZZ sex determination

System in which females are typically ZW and males ZZ

Haplodiploidy

System in which fertilized diploid eggs typically develop as females and unfertilized haploid eggs as males

Complementary sex determination

Sex-determination system in which genotype at particular loci influences sexual development

Doublesex, transformer, and fruitless

Recurrent downstream regulators involved in insect sex-specific development

Wolbachia manipulation

Reproductive changes caused by Wolbachia bacteria that can alter host sex ratios or reproduction

Monogamy

Mating system in which an individual mates with one partner

Polygyny

Mating system in which a male mates with multiple females

Polyandry

Mating system in which a female mates with multiple males