ENT201 - Exam 2

Fertilization

Most insects practice internal fertilization through copulation (Direct transfer from aedeagus to vagina)

Primitive insects such as Zygentoma and Archaeognatha practice indirect fertilization with a spermatophore

Sex Determination

XX → female

XY or X → Male

Opposite for Butterflies and Moths

Bees and Ants are haploid (XX, female) or diploid (X, male)

What Happens to the Eggs?

Oviparous - lay an egg

Viviparous - living young

Ovoviviparous - lay it, it hatches immediately

Courtship and Mating

Males do the advertising, females do the choosing

Babies are on their own after birth

Except Social Ones

Order of the Day - Orthoptera 

Entymology:

• Ortho → straight

• ptera → wings

Taxonomy:

• Caelifera: grasshoppers, locusts

• Ensifera: crickets, katydids

• 20,000 species globally distributed

Morphology:

• Cylindrical body

• Elongated hind legs

• Biting/chewing mouthparts

• Large compound eyes

• Multi-jointed, filiform antennae

Life

• Hemimetabolous (Incomplete Metamorphosis)

• May be diurnal or nocturnal

• Phytophagous (eat plants) or omnivorous

• Stridulation (males stridulate)

• No wings = nymph!

Order of the Day - Coleoptera (Beetle)

Etymology

• koleos - sheath

• pteron - wing

Taxonomy

• 400000 species found everywhere

• 40% of all arthropods

• 25% of all known animals

• Rove beetles, scabs, blister beetles, weevils, fireflies, stag beetles

Morphology

• Elytra: modified forewings that form a protective case for hindwings → reduced, lost, or fused in certain groups

• Hind wings large, membranous, folded beneath the elytra

• Tarsi 2 - to 5-segmented

• Chewing mouthparts

Life

• Holometabolous (Complete Metamorphosis)

• Forensic and medical importance

• Mating/courtship variable

• Lifespan variable

• Highly variable ecology

Order of the Day - Hemiptera (Insect)

Entymology

• Hemi - half

• Pteron - wing

Morphology

• Forewings hardened at base but membranous at the ends (hemelytra)

• Hindwings membranous

• Piercing/sucking mouth parts: rostrum

• Tymbal organs or tibial combs for those that produce sound

• Cicadas, Aphids, Assassin bugs, Leaf hoppers, Tree hoppers, Moss bugs, shield bugs, etc.

Taxonomy

• Sternorrhyncha - Small; sedentary/sessile

Life history

• Largest order of hemimetabolous insects

• Some parthenogenetic species

• Some aphids are viviparous

• Majority phytophagous

• Filter organ to deal with excess water

• Some are hematophagous

• Majority terrestrial

• Lifespan can vary greatly (1 month to 17 years)

Order - Non-Insect Hexapods (Class ENTOGNATHA)

• Six legs, primitively wingless, three body regions, entognathous (chewing mouthparts tucked inside head capsule)

• Protura, Collebola, Diplura

Order - Class Insecta

APTERYGOTA: Primitively wingless insects

PTERYGOTA: The winged insects

• PALEOPTERA (unable to fold wings over abdomen) → Mayflies (All aquatic) & Dragonflies

• NEOPTERA (wings fold over abdomen) → Three categories:

1. POLYNEOPTERA (EXOPTERYGOTA - wings on the outside) → Chewing mouthparts, simple metamorphosis, cerci

2. PARANEOPTERA (EXOPTERYGOTA - wings on the outside) → Simple metamorphosis, no cerci, diverse mouthparts

3. HOLOMETABOLA (ENDOPTERYGOTA - wings on the inside) → Undergo complete metamorphosis

Muscles

• They can only do one kind of work → Pull

• Fuel - carbohydrates, lipids and oxygen

• Insect muscle is translucent

• Visceral muscle —> move internal parts

• Skeletal muscles —> move body parts

Movement of Appendages

• Often "opposing" muscles to “open” & “close”

• Assisted by rubbery hinges (resilin)

• Muscles stimulated by nerve impulses → synchronous (1:1 relationship between nerve impulse and muscle contraction) or asynchronous (contract multiple times for a single impulse)

Flight

Hot muscles required, but not too hot → 85 to 105

Use abdomen as a radiator

Takeoff in the wind

Most insects have indirect flight muscles

• Wings are attached to walls of thorax → change shape of the thorax to make wings go up and down

• Frequency varies from 10 to 1,000 beats/second

Insect flight is very efficient

Migration

Nomadic migration → Movement of large numbers of individuals

One-Way Annual migration → South to North in summer

Two-way annual migration → North to South in winter

Monarch migration —> endangered

Sound Communication

Stridulation → file and scraper

Tymbals → found in cicadas → Reinforced plates of exoskeleton

Percussion → bang their heads against wall

Hissing and whistling → Death’s head moth

Wing beating

Vast majority of insects are deaf

Visual Cues

Swarming, wing flapping, color flashing

Bioluminescence (production of light by living organism) and fireflies → doesn’t generate waste heat

Chemical Communication

1. Allomone → chemical produced by ones species and detected by a different species. Benefits the sender and harms the receiver.

2. Kairomone - chemical produced by ones species and detected by a different species. Benefits the receiver at the expense of the sender.

3. Pheromone - chemical produced by ones species and detected by other members of the same species. Usually benefits both sender and receiver:

• Sex attractants

• Alarm pheromones

• Dispersal pheromones

• Aggregation pheromones

• Caste determining pheromones

• Marker pheromones

• Trail marking pheromones

Heiarchy of Social Organization

Insects are vastly solitary → ex) praying mantis

Subsocial → Mated pair take care of a cohort of offspring

Communal organization → one life stage lives together, rest of life cycle is solitary → ex) caterpillars and ringworms

Semisocial → reproductive division of labor → one female lays eggs, everyone else takes care of eggs

Eusocial → truly social → reproductive division of labor, overlapping generations → ex) ants, termites, bees

All exhibit polymorphism

Fate of colony depends on queen

All practice trophallaxis

All practice extensive grooming

When you want to re-queen hive, use piece of candy, then over time the queen will smell like everyone else, and they won’t kill her

All species make complex nest structures

All have wings as reproductives

Swarming → All colonies send their reproductives at the same time

Differences Among Termites, Bees, and Ants

Termites and Bees → vegetarians → Ants basically eat everything

Termites male reproductive → king

Ants and Bees → queens mate one time → they only produce males when they need to

MOSTLY FEMALE (95%) in Bee and Ant colonies

Termites → (XX) (XY) so its a even split between male and females

Termites → simple metamorphosis

Bees and Ants → complete metamorphosis

Insects are Beneficial

Vast majority of insects are neutral or good, and without them we would not survive

Producers

Honey bees → honey, beeswax, royal jelly, pollen

Silkworms → domesticated, we take their silk → they only eat mulberry leaves

Scales → Shellac → furniture finish and edible

Gall wasps → permanent black ink

Suppliers

Entomophagy is ubiquitous among animals

Prey for carnivorous plants

Pollinators -→ vast majority of vegetables and fruits we consume are pollinated by insects

Pollinators

Most plants are pollinated by insects

Bees of course, but also ants, wasps, beetles, flies, mosquitoes, moths, etc

Allies

Insects are allies against pests in agriculture

Decomposing

Ultimate recyclers - turn dead and decaying plants and animals and their waste products into reusable sources of C, H, N, O, P, etc.

Trees and other plant material - termites, beetles, flies, ants, spring tails, etc

Animal carcasses - flies, hide beetles, burying beetles, mealworms, etc.

1. Forensic entomology - insects determine time of death

2. Surgical maggots - conduct surgery, use right species

Animal waste - maggots and dung beetles

Science

The perfect “guinea pigs” for experiments

Annoyance with No Injury

Screaming crickets, creepy crawlers, and ugly smelly roaches

Level of annoyance varies with individual and insect

Entomophobia - an irrational fear of all insects

Delusional parasitosis - belief that non-existent insects are crawling on or biting one's body

Insects Causing Direct Pain

Defensive weapon → Urticating hairs, sharp mandibles and spiny legs → Harmless if you don’t mess with them

Blood-sucking flies →

1. Mosquitos, flies others

2. They need blood for eggs

3. Only females bite

4. Mouthparts may needle in or cut and slash

Venemous →

1. All centipedes are venomous

2. Spiders → neurotoxic venom, web-builders

3. Brown recluse (spider) → non-web builders, non-aggressive

Stings (Hymenoptera) →

1. Velvet ant → most painful sting

2. Wheel bug → most painful bite

Parasites →

1. Anoplura - Head lice and nits - Cooties and crabs - feeling lousy

2. Acarina - itch mites and follicle mites

3. Diptera - myiasis → The invasion of living tissue

4. Hemiptera - bed bugs, people and chickens

5. Siphonaptera - fleas (only adults bite us) and dogs

Allergies and Reactions

German cockroaches → important for a source of allergens

Dust mites → difficult to deal with

Anaphylactic shock → Response to venoms, anesthetics, anticoagulants