UCR Entomology 010 Midterm #1

Abdomen Structures & Functions

Structures: Cerci & Spiracles

Functions: Reproduction system, Respiratory system, Digestive system, and Excretory system

Ametabolous Development

Young and Adults look similar and molt to become larger

Annelida

Sub-phylum that includes worms. Bilateral symmetry, Breathe through skin, Have blood vessels (closed circulatory system), Bristles on segments to aid in movement

Antenna Types

Geniculate: looks like an elbow, found on social insects (Ants and Bees)

Plumose: looks like a bottle brush (Mosquitoes)

Aristate: big pieces of antennae segments with hair on end (Flies)

Aposematic Coloration

Anti-predator adaptations, color warning signals

Arthropoda

Phylum that is comprised of invertebrate animals including insects, spiders, crustaceans, and their relatives. They have segmented body, external skeleton, jointed limbs, open circulatory system. Proto-annelid is theoretical ancestor

Auditory Receptors

Tympanal Organ: senses frequency, intensity, and temporal characteristics of sound stimuli.

Johnston's Organ: Detects vibrations impacting the flagellum, helps insects manage flight

Used to locate mates and detect enemies

Binomial Nomentclature

Genus & species, both italicized. Species is lowercase. Three domains in tree of life are: Bacteria, Archaea, Eukaryotes. Order is Kingdom, Phylum, Class, Order, Family, Genus, Species

Biodiversity and Abundance of Insects

About 1 million insect species, 1.9 species in total. Billions of insects per person

Body Design of Insects

Insects have three segments: Head, thorax, & abdomen. Thorax holds wings and legs. Head is for eating and sensory processing. Abdomen is in charge of reproduction, respiration, digestion, and excretion.

Book Lungs

A type of respiratory organ used for atmospheric gas exchange in certain air-breathing arachnid arthropods (scorpions and some spiders). Located in the abdomen, "folded book" appearance

Centipede vs. Millipede

Centipedes: One pair of legs per segment, move round quickly, venomous fangs, carnivorous predators

Millipedes: Two pairs of legs per segment, move around slowly, excrete toxins on their cuticle, herbivorous

Cephalothorax

Head and thorax fused together. Legs are attached to this

Cerci

Paired appendages on the rear-most segments of many arthropods used as sensory organs/pinching weapons

Chelicerata

Sub-Phylum that is comprised of sea spiders, horseshoe crabs, spiders, scorpions, mites. Two body regions: cephalothorax and abdomen. First appendage is chelicerae. Males have pedipalp used for mating. 4 pairs of legs. Simple single-lensed eyes. Book lungs/gills to breathe.

Chemoreception

Taste and Smell receptors

Taste: Detects chemicals in fluids and on surfaces, receptors found on mouthparts, foregut, and tarsi

Smell: Detects chemicals in the air, receptors found on or near antennae

Functions: Determine if host is appropriate, sexual signaling and mate locating, trail marking, and alarm or defense communication

Closed Circulatory System

Blood circulates in the veins or ducts of the system (Like Humans)

Compound Eye

Eye with multiple lenses, each individual lens is called an "ommatidium"

Crustacea

Sub-Phylum that is comprised of lobsters, crabs, shrimps, barnacles, isopods. Mostly aquatic animals, but can be terrestrial. 5 pairs legs. 2 pairs antennae. 2 body regions; cephalothorax and abdomen. Biramous legs.

Diapause

A period of dormancy in which many insects undergo to avoid adverse conditions (winter cold, absence of food) happens during any stage of metamorphosis.

Different Types of Metamorphosis

Ametabolous (Primitive): Adults look basically identical to nymphs (silverfish, bristletail)

Hemimetabolous (Simple Metamorphosis): Adults look like nymphs except for wings

Holometabolous (Complete Metamorphosis): Adults look very different from larvae, presence of pupal stage

Dorsal Vessel

Insect Heart

Ecdysone

Hormone that causes molting. Comes from the prothoracic gland

Ecological Implication of Insect Metamorphosis

Ametabolous: All life stages in same habitat

Hemimetabolous: All life stages tend to be in similar environments and eat similar foods

Holometabolous: Larvae are frequently in very different habitats and eat different foods from adults; larval insects and adult insects occupy very different ecological niches (little or no competition)

Exuviae

The skin or old cuticle that is shed during molting

Fat Body

Functions: Group of cells that store nutrients; Metabolism and detoxification; Processes any toxic food; Most analogous to the human liver

Function of Insect Body Regions

Head: Mouthparts, Eyes, & Antennae

Thorax: Wings & Legs

Abdomen: Respiratory system, Reproductive system, Digestive system, & Excretory system

Gas Exchange

The use of the tracheal system to provide oxygen to the insect's body

Head Structures & Functions

Structures: Mouthpart (Clypeus, Labrum, Mandible, Maxille, & Labium), Eyes (Compund Eyes, Ocelli, Stemmata), Antennae

Functions: Consume food, sensory organs

Hemimetabolous Development

Simple Metamorphosis: Adults look like nymphs except for wings

Hexapoda

Sub-phylum that includes insects. Not all are insects though.

Example: class Entognatha- may be polyphyletic and have internal mouth parts. Protura: cone headed soil organisms. Diplura: two-pronged bristletails. Collembola: springtails. Furcula: "jumping fork"

Holometabolous Development

Complete Metamorphosis: Adults look very different from larvae, presence of pupal stage

Hormonal Regulation of Insect Metamorphosis

Molting between larval instar: ecdysone + High concentration of juvenile hormone

Molting from larva to pupa: ecdysone + Low concentration of juvenile hormone

Molting from pupa to adult: ecdysone + absence of juvenile hormone

Insect Body Size

Insect's small size helps them avoid predators, use less resources to survive, and have niche availability

Insect Brain

Used for memory and learning, controls social behavior

Protocerebrum - connected to eyes, receives signals from insect's eyes

Deutocerebrum - connected to insect antennae - connected through antennal nerve

Tritocerebrum - connected to insects mouth parts through the suboesophageal ganglion

Insect Digestive System & Ailmentary Canal

Comprised of the Foregut, Midgut, and Hindgut

Foregut: Main function is the temporary storage of food. Little bit of digestion occurs

Midgut: most of the digestion and nutrient absorption occurs

Hindgut: used for water absorption

Insect Excretory System

Filamentous blind sacs that filter the hemolymph of metabolic wastes and transfer the wastes to the

hindgut.

Insect Hemolymph

Insect blood (can be brown, green, or clear)

Insect Leg Structure & Types

Structure: Coxa, Trochanter, Femur, Tibia, Tarsus, Claws

Types: Cursorial (Running), Natatorial (Swimming), Raptorial (Grabbing), Fossorial (Digging), Saltatorial (Jumping), Corbicular Hairs (Pollen Basket)

Insect Metamorphosis

Change from immature to adult, Involves multiple changes in form during development

Egg, Nymph, Larva, Pupa, Adult (not all species have these stages)

Insect Molting Process

Sensory Input (Exoskeleton is too small), Brain Hormone (Stimulates the prothoracic glands), Prothoracic gland, Ecdysone (causes molting)

Insect Tagmata

The name of the three body regions of an insect

Insect Wing Structure & Types

Structure: "Classic" shape is two wings on the mesothorax and two on the metathorax. Halteres are used as gyroscopes while in flight

Types: Twisted wings (Strepsiptera), Fringed wings (Thrips)

Insects as Human Food or Animal Feed

Easy to find, more than ½ is edible. Less greenhouse gas produced and less ammonia. High conversion efficiency. Little animal welfare issues. Low risk of transmitting zoonotic infection.

Instar

Phase between 2 consecutive moltings (3-4 days) A developmental stage of arthropods

Male & Female Reproductive Organs

Male: Spermatophore, Testis, Seminal Vesicle, Aegeagus (Allows Entomologists to differentiate between different species)

Female: Spermatheca, Ovaries, Ootheca

Male Accessory Glands

Used to make protein rich spermatophores/accessory structures

Malpighian Tubules

Organ following the midgut that filters out salts from the hemolymph (analogous to kidneys)

Mechanoreceptors

Sensing of vibration or mechanical stimuli

Modifications of Insect Wings

Tegmina on grasshoppers, act as protection

Elytra on beetles, can hide under shell

Hemelytra on stink bug/true bug, have half leathery and half clear portion

Molting

Behavioral process that results in the shedding of old cuticle (exuvia) and regeneration of a new one. Allows for insect growth.

Monophyletic Group

Two groups that share the same common ancestor and all descendant species. This group is the natural group.

Ocelli

Single lens eyes on the top of the head, not sides. Used to detect light

Ommatidia

Light sensing units of the compound eye

Onychophora

Sub-phylum comprised of velvet/walking worms. Bilaterally symmetrical. Gas exchange via trachea. Open circulatory system. Exoskeleton. Link between worms and arthropods. Live in moist environments. Stubby legs, stubby antenna, small eyes jaws surround mouth

Open Circulatory System

No veins. Hemolymph sent from posterior end of the animal to anterior via the dorsal vessel and aorta. Circulates to the rest of the body and "washes" over organs

Ostia

Holes in the dorsal vessel (heart) that allow hemolymph to flow in.

Parthenogenesis

Asexual reproduction. Offspring are genetic copies of mother.

Polyphyletic Group

Grouped by having common characteristic, but they do not share a common ancestor

Provetriculus

Grinding organ that grinds and processes food before it enters the midgut. Also known as the "gizzard"

Reason to Study Insects

Because it's a GE, because they are everywhere, uses in medicine

Reasons for the Evolutionary Success of Insects

Flight. Metamorphosis. Sociality. Small size. High fecundity. Fast generation time. Exoskeleton (integument)

Rectum

Used to remove waste from the body

Reflexive Bleeding

Defensive mechanism in some insects where a noxious fluid is exuded. Bitter fluid, including hemolymph and noxious chemicals

Relationship Among Taxa

Phylogeny- branch of biology that deals w/phylogenesis.

Phylogenesis- evolutionary development and diversification of a species or group of organisms, or a particular feature of an organism

Monophletic group- contains the common ancestors of all of its descendent species

Respiratory Organs

Trachea & Spiracles

Sexual Selection vs. Natural Selection

Occurs through "choices made between sexes" and "competition within same sex". Mode of natural selection in which some individuals out-reproduce others of a population because they are better at securing mates

Sociality in Insects

Cooperation in brood care/Nest Maintenance

Overlapping generations between mother and adult offspring

Division of labor within colonies (different chores are divided within the colony based on age). Allows for insects to be much more efficient considering short lifespans, separation of labor nullifies class hierarchy

Spermatheca

Sperm storing organ in females. In virgins, it's flesh colored but in fertilized ones, it's white. Has special ability to keep sperm alive for a long time

Spermatophore

Protein rich sack that carries sperm when transferred from males to females. Created by the accessory glands

Spiders

Not insects, Cephalothorax and Abdomen. Part of the sub-phylum chelicerata

Stadium

Duration of a particular instar

Stemmata

Eyes on side of head, singular lens eyes, usually on immature insects with complete metamorphosis

Benefits of Complete Metamorphosis

Larvae are frequently in very different habitats and eat different foods from adults: larval insects and adult insects occupy very different ecological niches (little to no competition)

Structure of Insect Exoskeleton

Suture: lines on the insect

Pits / sculptures on the surface: indentations on the insect, mechanical structures

Setae (Seta): "hairs", Number, arrangement, or patterns of setae determine species

Scales: modified, flattened setae, most common in butterfly and moth wings (caddisfly which is a close relative still has baby wings

Epicuticle (wax layer): helps to maintain body water retention

Procuticle (Exocuticle + Endocuticle): thicker portion of cuticle, consists of chitin (polymer of a sugar), outer portion is exocuticle and endocuticle is inner portion- living cell, everything in layers before is dead; cells are responsible for making chitin, hairs, wax, etc.

Epidermis: Inner layer on insect onto which muscles attach

Chitin: long chain polymer of glucose (sugar) and is a characteristic component of exoskeletons in crustaceans and insects

Apodeme / Apophysis: points for muscular attachment and provides structural support for insect's body

When skin is shed, only epicuticle and exocuticle is molted

Structures on Insect Abdomen

Spiracles, reproductive organs, digestion, cerci. Can have up to 12 segments functioning in tagma

Cerci (singular: cercus): appendages that are found at the tip of the abdomen

Spiracles and tracheal system

Found in caterpillars and other larvae on the underside

Connects outside insect with inside of insect, allows for oxygen to enter the insect

Allows for unidirectional airflow

Reproductive organs: found within the abdomen

Territorial Behavior

Males hold territories for females to get competition. These territories are oviposition sites, foraging sites, nesting or emergence sites, advantageous habitats

Thorax Structures & Functions

Structures: Wings & Legs

Function: Movement such as walking or flight

Tracheal System

Gas exchange occurs in this system via spiracles to exoskeleton to trachea to tracheal branches to tracheole. This system has a chitin lining, very complex tubing within the body

Types of Mimicry

"Classic" Mimicry: An insect blends in with its surroundings. Ex. Leaf insects, stick insects

Batesian mimicry: An unprotected species (mimic) evolves to look like a protected species (model)

Mullerian Mimicry: A chemically protected species (mimetic #1) evolves to look like another protected species (mimetic #2)

Ventral Nerve Cord

Makes up part of the central nervous system. It usually consists of the segmental ganglia anteriorly with the nerve cords running down the ventral plane of the organism.

What is Evolution?

The development of new types of living organisms from pre-existing types, the accumulation of genetic difference in a population over long periods of time

What is an Insect?

Consists of a segmented body, jointed legs, and an exoskeleton

Why Study Insects?

Prehistoric roots / cultural importance / agricultural importance / medical / veterinary importance / urban & structural importance