Entomology Midterm Practice

Hexapoda (insects)

• 2-30 million

• monophyletic (origin of shared, derived trait

• cambrian explosion

phylum arthropoda

• main extant groups of arthropods: insects, crustaceans, myriapods, chelicerates

• body segmented with jointed paired appendages, repeated tagma segments

5 main groups (subphylum) of phylum arthropoda

1. trilobitomorpha (extinct)

2. crustacea

3. hexapoda (mostly Insecta)

4. myriapoda

5. chelicerata - arachnids and allies

subphylum chelicerata

• 1st pair of appendages: chelicerae 

• developmentally different mouthparts

• 2 tagma: cephalothorax and abdomen 

subphylum crustacea

• 1st 2 pairs of appendages modified into sensory organs like antennae

• 7 pairs of walking legs

• 2-3 body regions 

subphylum myriapoda 

• class chilopoda and diplopoda (centipedes and millipedes) 

• 1st pair of segments = antennae

• mouthparts are mandibles instead of chelicerae 

subphylum hexapoda

• 3 body regions: head, thorax, abdomen

• 3 pairs of walking legs 

• 1st pair of appendages are antennae 

evolutionary success of Hexapoda

• Long evolutionary history - among earliest land colonists

• High rates of evolution - large populations, short gen. times

• Small body size - many ecological niches

• Flight - escape and migration 

• Diapause - resting stages which endure unfavorable conditions

• Complete metamorphosis - separate feeding lifestyles for larvae and adults

• Exoskeleton - great adaptability

Hexapod groups 4 significant develpment events

1. position of mouthparts (entognatha vs extognatha

2. presence of wings (apterygota vs pterygota

3. wing folding (paleoptera vs neoptera

4. development of complete metamorphosis (exopterygota vs endopterygota

3 basic types of metamorphosis

1. ametabolous - no metamorphosis. entognatha, apterygota

2. hemimetabolous - incomplete metamorphosis. paleoptera, exopterygota

3. holometabolous - complete matamorphosis. endopterygota 

Endopterygota (holometabola) 

• complete matamorphosis

• egg > larva > pupa > adult

• larva looks different from adult

• wings develop internally during pupal stage

• beetles, butterflies, flies, bees

exopterygota

• incomplete metamorphosis

• egg > nymph > adult

• nymph resmbles adult but lacks wings and sexually immature

• wings develop externally as wing pads

• grasshoppers, cockroaches, true bugs, dragonflies 

entognatha

mouthparts surrounded by head capsule

• collembola

• diplura

• protura 

Ectognatha (Insecta)

great majority of hexapods

• apterygota (primarily wingless)

• pterygota (ancestor with wings) 

Order Collembola - sprintails

• 3 tagmata

• 3 pairs of legs

• Furcula, tenaculum, collophore

• Encapsulate mouthparts

• No tracheal respiratory system

• Indirect copulation

Order zygentoma - silverfish, apterygota

• Wingless, flattened

• Long antennae

• 3 equally long filaments

• Small or absent eyes

• Scavengers

  • Under bark

  • Urban settings

Order ephemeroptera - mayflies (paleoptera infraclass)

• Large fore wings, small hing wings

• Very short antennae

• Adults have 2 or 3 cerci

• Larvae: gills

Order odonata - damselflies, paleoptera

• Large eyes

• Predatory

• Arvae: external gills at the end of abdomen

• Slender abdomen

• Wing folded at rest

Order odonata - dragonflies, paleoptera

• Large eyes

• Predatory

• Larvae: internal gills at the end of abdomen 

• Wide abdomen

• Wing held open at rest

Order grylloblattodea - orthopteroids, icebugs/ice crawlers - exopterygota

• Incomplete metamorphosis

• Wingless

• Cold adapted

• Snow pack, glavier, ice cave

• 3 places on earth: pacific northwest, east asia, rocky mountains in northern us and canada. Canadian national insect

Order phasmatodea - the orthopteroids, walking sticks, exopterygota

Masters of camouflage

Order orthoptera - the orthopteroids, grasshoppers, crickets, katydids 

• 1st pair of wings robust and leathery (tegmen)

• 2nd pair of wings membranous

• Stridulation

• Saltatorial hind legs

Order mantodea - orthopteroids, praying mantids

• Exopterygota

• Enlarged for legs

• Movable head

• Voracious female

• 2 spp introduced, 1 sp native

Order blattodea - cockroaches

• Round bodies

• Round pronotum

• Long antennae

• Around 30 spp associated with human habitats

Order blattodea infraorder isoptera (termites)

• Eusocial insects

• Parental care

• Division of labor (caste) - workers, soldiers, queens

• Digest wood-fiber (symbiont protists) 

• Exopterygota

chelicerata appendages

• no antennae

• chelicerae (mouthparts)

• pedipalps (small limbs used in sex and or feeding) 

• 8 walking legs 

mandibulata

basic mouthparts: mandibles, maxillae

tagma / tagmata

• specialised grouping of multiple segments

• head, thorax and abdomen

prognathous

mouth parts positioned forward

hypognathous

mouthparts positioned downward

ophistognathous

mouthparts positioned backward

tentorium / endoskeleton

internal cutivular structure for muscle attachments and strength

filiform antennae

plumose antennae

thorax segments

• prothorax

• mesothorax

• metathorax

exoskeleton (integument)

• protects internal organs and tissues

• protective and preventative barrier

• needs to be molted to allow growth

ectodermal tissue (foregut)

• cuticular lining

• ingests, processes food

endodermal

• secretion, absorption

• midgut

ectodermal tissue (hindgut)

• cuticular lining

• absorption, excretion

peritrophic membrane

• very efficient high flux sieve

• selectively transports substances through the membrane 

insect guts

foregut

• store ingested food 

• fermentation chamber in scarab larvae

midgut

• columnar and secretory cells

• mycetomes house bacterial symbionts, help with digestion

• filter chamber: midgut modified for liquid diets, honey dew

hindgut

• malpighian tubules primary organ for excretion 

fat bodies

• center of metabolism

• analogous to vertebrate liver 

• storage, synthesis, breakdown, release nutrients

hemocytes

insect blood cells, no O2, protection, transfer hormonal products

tracheal system

carries oxygen in and C02 out

reproduction methods

• swarming - mayflies, scarabs

• hilltopping - butterflies

• nuptial gifts, short range courtship

sex pheromones

females produce, males detect plume

male reproduction systems

1. production, storage and delivery of sperm

2. supply female with nutrients

3. regulate female fecundity

spermatophore

protein envelop that contains sperm 

spermatophylax

a non sperm portion of spermatophore eaten by female

female reproduction systems

1. production of eggs

2. sperm reception/storage

3. fertilization

4. oviposition 

vitellogenesis

development of egg cells 

oogenisis

nutrient moved into the eggs

oosorption

eggs are resorbed

neuron

cell type that transmits information

action potential

occurs when a neuron sends information down an axon

dendrite

where nerve impulses start, an energy transducer. converts light, chemical, or physical kinetic energy to electricity 

3 types of neurons

1. monopolar

2. bipolar

3. multipolar

central nervous system (CNS)

brain + subesophageal ganglion + ventral nerve cord

visceral system (VS)

corpus cardiacum + corpus allatum (controls guts, endocrine organs, reproductive and treacheal systems) 

insect sensory systems

1. photosensilla (vision, UV, photoperiod)

2. mechanosensilla (hearing, touch)

3. chemosensilla (smell, taste)

4. thermosensilla (IR infrared detection)

5. hygrosensilla (humidity) 

photosensilla - sight

• specialized structures sensitive to light

• stemmata, ocelli, compound eyes

mechanosensilla - hearing

• exocuticular, endocuticular

• trichogen, tormogen, sense cells

scolopale

actual transducer that converts mechanical energy to nerve impulse

sounds percieved by mechanosensilla

• mate attraction, species recognition (differences in stridulation songs), antipredator adaptations

chemosensilla

• smell, taste

• odor receptor: generally located in insect antennae, setae with many pores

• taste receptor: uniporous, fewer nerve endings. mostly located in maxillary and labial palps 

role of pheromones

• sex

• aggregation

• alarm

• trail

• host marking

pheromones

chemicals that induce behavioural or developmental responses between individuals of the same species

thermosensilla

pyrophilic insects have infrered receptors

hygrosensilla

detect changes in air moisture

impacts of severe defoliation

• reduction in photosynthesis

• interference of transpiration 

• interference of food translocation

• root mortality because of disruption of nutrient movement

defoliators

• lepidoptera (larval butterflies and moths)

• hymenoptera (larval sawflies, leaf cutting ants)

• diptera (larval flies with leaf and bud mining habits)

• coleoptera (adults and larvae esp leaf beetles and weevils)

• phasmatodea (walking sticks and leaf insects)

• orthoptera (katydids)

lepidoptera

scales are modified and flattened setae

lepidoptera vs hymenoptera

lepidoptera: 5 or less prolegs

hymenoptera (sawfly): more than 5 pairs prolegs

family gracillaridae (defoliators) - leaf miners and blotch leaf miners

• larvae develop within the leaf

• univoltine, not economically important

• premature leaf drop

• pattern of leaf mine and host plant can be diagnostic

family coleophoridae (defoliators) - casebearers

• leaf mining > construct a case

• exotic invader from europe

• outbreaks can last up to 10 yrs

family Psychidae (defoliators) - bagworms

• cedar, juniper, white pine

• make bags as soon as they hatch

• females stay in bag and lay 500-1000 eggs

family Cossidae (defoliators) - carpenterworms

• attacks hardwoods, poplar

• 2-4 years development

• 200-800 eggs in bark

• no defoliators

family Erebidae (defoliators) - subfamily arctiinae

moths

family Notodontidae (defoliators) - prominents

• gregarious feeders as early instars

• various hardwoods 

family Nymphalidae (defoliators)

• elms, poplars and willows

• gregarious feeding of entire branches

• camouflage 

family Saturniidae (defoliators) - giant silkmoths

• not economially important

• distinctive feeding pattern (consumes entire leaf then cuts petiole)

family Sphingidae (defoliators) - hawkmoths and hornworms

• aerodynamic, good fliers

• larva have horns

family Sesiidae (defoliators) - clearwing moths

• transparent wings 

• transverse yellow/orange bends across abdomen

• long narrow forewings

defoliators big 5

1. leaf rollers

2. budworms

3. tent caterpillars

4. loopers/inchworms

5. spongy moth

family Tortricidae (defoliators) - leafrollers and budworms

• eastern and western spruce budworm

• large aspen tortix

family Lasiocampidae (defoliators) - tent caterpillars

• communal tent spinning

• thermoregulation

• mass anti predator displays

family Geometridae (defoliators) - loopers and inchworms

• 2-3 pairs of prolegs at end of abdomen, move by looping

family Erebidae (defoliators) - tussock moths

• sexual dimorphism

• some of most costly forest pests