External & Internal Insect Anatomy / Insect Taxonomy & Systematics

Basic elements of the insect exoskeleton

-Composed of a cuticle that covers the body and is secreted by the epidermis
-protects against dehydration, abrasions, and attack from predators
-mostly chitin with other proteins and waxes

Axes of the insect body

-Longitudinal
-Transverse
-Dorsoventral

Parts of insect head

Head regions (sclerites) separated by sutures
-antenna
-compound eye

Insect mouthparts and their orientation

-Labrum (upper lip)
-Hypopharynx (tongue)
-Mandibles (jaws)
-Maxillae
-Labium (lower lip)

Elements of the insect antenna (proximal to distal)

-Antennal sclerite
-Scape
-Pedicel
-Flagellum

Basic antennal types

-Filiform (threadlike)
-Serrate (saw-toothed)
-Geniculate (elbowed)
-Moniliform (beadlike)
-Pectinate (comb-shaped)
-Plumose (plume-like)
-Capitate (knoblike)
-Flabellate (fan)
-Aristate (bristle-like)
-Lamellate

Insect leg segments (proximal to distal)

-Coxa
-Trochanter
-Femur
-Tibia
-Tarsus
-Pretarsus

Insect leg modifications

-Raptorial (grabbing)
-Saltatorial (jumping)
-Cursorial (running)
-Fossorial (digging)
-Natatorial (swimming)

Hydrostatic Exoskeleton

Soft-bodied adults/larvae maintain turgidity by criss-crossed body wall "turgor" muscles that continuously press against the incompressible hemolymph of the hemocoel - foundation for other muscles

What is the tripod of legs?

Continuous contact with the ground - fore/hind legs on one side move with middle leg on the opposite side

What type of muscles do insects have? How are they attached to the exoskeleton?

-Striated muscle consists of overlapping layers of protein molecule
-Via tonofibrillae link to epidermis

Compare direct and indirect flight muscles. How does each type move the insect wing?

Direct: muscle attached directly to wings
Indirect: no muscle-wing connection; muscle action deforms throax by moving notum up/down to move wings

The basic elements of the central nervous system

Series of ganglia joined by paired longitudinal nerve cords lying ventrally in body cavity

The two ganglionic centers of the insect head and the function of each

Brain: associated with vision, innervates antennae handles signals from body
Subesophogeal Ganglion: innervates mouthparts

The four insect endocrine centers and their functions

Neurosecretory Cells - modified neurons found throughout the nervous system
Corpus Cardiacum - pair of neuroglandular bodies located on either side of aorta; stores/release neurohormones
Prothoracic Glands - secrete ecdysone (elicits molting)
Corpus Allat

Functions of important insect hormones

Ecdysteroids - steroids that promote molting
Juvenile hormones - control metamorphosis and reproductive development
Neurohormones - protein messengers regulating development, homeostasis, metabolism, and reproduction

Basic elements of the open circulatory system in insects

Dorsal vessel
-anterior dorsal vessel
-posterior dorsal vessel
-ostia dorsal vessel

Basic elements of the insects respiratory system

Gas exchange
Trachea - air enters trachea vis spiracles
Maximum of 10 pairs
+2 thoracic
+8 abdominal

Closed vs. Open tracheal systems

Open: valved spiracles open directly to environment
Closed: no spiracles, closed to environment; gas exchange occurs directly through cuticle
i.e. open (cockroach) closed (dragonfly naiad)

Three basic regions of the alimentary canal

Foregut, midgut, hindgut

Function of malpighian tubules

Primary organs of excretion & osmoregulation; act in concert with rectum and/or ileum

Primary structures of the female and male reproductive systems

Male: paired testes, paired vas deferentia, seminal vesicles, median ejaculatory duct, accessory glands, genitalia
Female: paired ovaries, paired oviducts, egg calces, common vagina, spermatheca, ovipositor
organ in the females (spermatheca) fertilization

Major contributions of John Ray and Carolus Linnaeus

John Ray: classified plants according to similarities and differences that emerged from observation - first to coin the term "species"
Carolus Linnaeus: grouped genera by shared similarities, introduced concept of binomial nomenclature

Year that marks beginning of zoological nomenclature

1758

Five reasons for classifying organisms

1. Communicate, store, and retrieve information
2. Create informed hypothesis
3. Understand shared evolutionary history of species
4. Help solve environmental and human welfare challenges

Eight basic taxa of zoological classification (large->small)

Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species

Define: Biological species concept

Species as members of populations that actually or potentially interbreed in nature

Basic elements of cladistics

Seeks to determine the relationships among a group of organisms (taxa) based on their evolutionary novel characteristics

Closest living relative of insects

Crustaceans

List two synapomorphies of hexapods

Three functional body regions, three segmented thorax, one pair of antennae

Most basic diagnostic feature that distinguishes Entognatha from Insecta

Basis of mouthparts hidden within head capsule