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Entomology Cheat Sheet by

Applied Entomology course of my university, summarized to help me study and pass the exam. I hope it will be useful for you too.

Binomial Nomenc­lature

Domain
Eukarya
Kingdom
Animalia
Phylum
Arthropoda
Class
Insecta
Order
Coleoptera
Family
Chryso­melidae
Genus
Leptin­otarsa
Species
Leptin­otarsa deceml­ineata
This example is for the Colorado potato beetle

Zoology - Ecdysozoa

Secretes the exoske­leton → discon­tinuous growth → molt (ecdysis), preceded by apolysis → displa­cement of the epidermis from the old exoske­leton
It includes:
Euarth­ropoda (Insecta, Crustacea, Myriapoda,
Chelic­erata, Trilob­ita*)
arthro­pod­-like Onycho­pho­ra,­Tar­digrada
Nematoda
Nemato­morpha
Priapulida
Kinorh­yncha
Loricifera

Phylum Arthropoda

Subphyla
Trilob­ito­morpha, Chelic­erata, Myriapoda, Crustacea, Hexapoda
Class
Entognata, Ectognata (Insecta)
Subclass
Aptery­gota, Pterygota

Origin of wings theories

Tergal origin hypothesis
Wings originated from an expansion of dorsal body wall (tergum)
Pleural origin hypothesis
Wings were derived from epicoxal hendites and exites
Dual origin hypothesis
Contri­bution of both tergal and pleural components during the evolution of insect wings

Insects' Ecosystem services

Provis­ioning
material or energy outputs
Carbon absorp­tion, control of pathogens, pest control, pollin­ation, soil fertility
Supporting
mainte­nance of ecosystem
decomp­osi­tion, seed dispersal, recycling
Regulating
direct­ion­ality of ecosystem processes
Cultural
educat­ional, spiritual, aesthetic value
bioind­icators
Pollin­ation have an economic value of $235 to $577 billion per year worldwide

Ecological species concept

Species=
Group of organisms that occupy the same ecological niche
This means that
species are kept separated by the selection for niche adapta­tion, not by the reprod­uctive isolation
Cons
Different develo­pmental species inhabit different ecological niches

What is a DNA Barcode

Short standa­rdized DNA markers for the taxonomic indent­ifi­cation
It has to be variable among species, not within species
They do not necess­arily meet the requir­ements for DNA metaba­rco­ding: many species have to be identified simult­ane­ously
Primers:
1. annealing region highly conserved within the target group
2. annealing region not conserved in non-target organisms

Sampling

Community DNA
DNA extracted from a pool of indivi­duals
Enviro­nmental DNA
Mixture of genomic DNA for example soil, litter, water
Homoge­niz­ation and filtering

eDNA

Interc­ellular DNA
from living cellls or living multic­ellular organisms
Extrac­ellular DNA
derives from cell death

Ecological factors

Stenoe­cious
→ organism that can tolerate a narrow range of variab­ility, it can live only in a restricted range of habitats
Euriecious
→ organism that can tolerate a wide range of variab­ility and can live in a wide range of habitats
Ecological niche
→ how a specie interacts within an ecosystem
Hutchinson (1957) → 2 forms of niche:
Fundam­ental niche = focused in the abiotic conditions in which a specie could exist with no ecological intera­ctions
Realized niche = popula­tion's existence in the presence of intera­ctions

Biotic potential

It's the maximum reprod­uctive capacity of an organism in optimal enviro­nmental conditions
It's limited by: unfavo­urable enviro­nmental condit­ions, inhibiting effects or predators, parasites, diseases
It's expressed as a % increase per year or as the doubling time

What limits the growth of popula­tions

Ecores­istance
space, food resources, abiotic factors, biotic factors
Biotic factors:
Intras­pecific or extras­pecific
Intras­pec­ific:
Compet­ition for food or reprod­uction
Diapause
it's an endoge­nously regulated dormant state to survire seasons of adverse condit­ions. It can be obligatory (genet­ically determ­ined) or facult­ative
Quiescence
immediate response to a change in the enviro­nment
Extras­pec­ific:
parasi­toids, predators, diseases

Insect­-plant intera­ctions

Direct defence
act directly on the phytop­hagous to reduce the feeding perfor­mance. Example: Anti-n­utr­itional factors (induced) and Antixe­nosis or physical barriers (const­itu­tive)
Indirect defence
attract natural enemies of the phytop­hagous. Example Synomones (induced)
1. insects sense plant's Volatile Organic Compounds by odorant binding proteins to select approp­riate hosts

2. sucking insects cause minimal damage, while chewing insects cause wounding. They secrete proteins to suppress plant's defense response

3. many enzimes and transp­orters are involved. Plant derived toxic compound can be degraded by insect enzymes

Functional classi­fic­ation of pests

Not considered pests
their feeding activity does not cause economic damage
Occasional pests
occasi­onally cause damage due to abiotic factors
Key pests
relevant economic damage
Induced pest
They can become dangerous usually after changes in the enviro­nment dued to human activi­ties, example: alloch­thonous insects, monocu­lture, broad range pesticides
Economic damage can be:
1. propor­tional to physio­logical damage
2. less than propor­tional to the physio­logical damage
3. starts at a certain point of the physio­logical damage

Supplement of metabolism

Symbionts provide
→ B vitamins (Blood is deficient)
→ sterols
→ essential amino acids (N recycling capabi­lity)
Common traits in p-symb­ionts:
- genome reduction (~ 5.5 Mb)
- High AT content
Functional comple­men­tarity with host and co-sym­biont genomes
- Evolut­ionary stasis

Integrated Pest Management

Definition
ecosystem approach to crop production and protection that adopts a combin­ation of strategies
Key points
identi­fic­ation of key pest
 
monitoring strategy
 
define thresholds
 
implement control strategies
 
evaluate results
Economic injury level = cost of control / (market value x loss)

IPM control categories

Agrono­mical practices
Crop rotarion
 
Cultivar choice
 
soil management practices
 
fertil­ization
Physical and mechanical approaches
Heat to treat food and seeds
 
Microwave to trear wood
 
Mechan­ically remove insects: light, traps
Agroch­emicals
pheromone based suppre­ssion: mass traps
 
pheromone based attract and kill
 
mating disruption with sexual pheromones
 
Auto confusion, auto steril­ization
Biological control
introd­uction of natural predators or parasi­toids
 
pathogens: bacillus thurin­gie­nsis, fungi, nematodes
Inocul­ative biological control: natural enemies are released in the enviro­nment
Inondative biological control: natural enemies are released repeately
Conser­vation biological control: habitat management to let natural enemies live
  

Evolut­ionary background

Nothing in biology makes sense except in the light of evolution (Theod­osius Dobzha­nsky, 1973)
+
...Nothing in evolution makes sense without a good (true) phylogeny
=
Nothing in biology makes sense without a phylogeny

Cuticle synthesis

Insecta and Crustacea have an exoske­leton
Tyr and Phe are precursor of an essential component of cuticle systhesis
An Endosy­mbiont provides Tyr and Phe to the host
The host regulates the load of Endosy­mbiont to achieve cuticle, then eliminates it through apoptosis and autophagy

Zoology - Insecta

4 pairs of cephalic appendages (1 pre + 3 post oral)
Exposed mouthparts
Size: 0.2 - 300 mm
30 orders: Archae­ognata + Zygentoma (Apter­igota) and Pterygota

Insect orders

Apterygota
Archae­ognata, Zygentoma
Pterygota
Epheme­roptera, Odonata, Plecoptera, Isoptera, Blattodea, Mantodea, Gryllo­bla­ttodea, Mantop­has­matodea, Phasma­todea, Embiidina, Orthoptera, Dermaptera, Zoraptera, Psocoptera, Phthir­aptera, Thysan­optera, Hemiptera

DNA Taxonomy

Definition
Process of naming and classi­fying organisms into groups, according to their simila­rities and differ­ences
DNA barcoding
a standa­rdized approach to identify organisms by the use of a DNA barcode
DNA barcode
Short DNA sequence taken from starda­dized portions of the genome, coding or not a protein
Origin
1977: the idea; 1996: the first DNA metaba­rco­ding; 2003: use of the term DNA barcoding; present: DNA barcoding, metaba­rco­ding, eDNA

Cryptic species

Morpho­log­ically indist­ing­uis­hable species that can be recognized only by molecular data

Molecular taxonomy

It merges BSC, MSC and Phylog­enetic species concept PSC

PSC considers monoph­yletic groups as the unique real entities of the speciation process

Types of taxon

Monoph­yletic taxon
A group of organisms including the most recent common ancestor and its descen­dants
Polyph­yletic taxon
A group of organisms in which the most recent common ancestor is not included
Paraph­yletic taxon
A group of organisms including the most recent common ancestor but not its descen­dants

DNA barcoding workflow

1. Sample collection
2. DNA extraction
3. PCRs
4. Sanger sequencing
5. Electr­oph­ero­grams
6. Comparison with database (BOLD, BLAST)
7.Iden­tif­ica­tion!

DNA metaba­rcoding workflow

1. Sample collection
2. Sample processing
3. DNA extraction
4. Libraries prepar­ation
5. Sequencing
6. Bioinf­ormatic analyses
7. Results

Note!

A reference database is mandatory in DNA analysis!

Homology, Orthology, Paralogy

Homology
2 genes that share a common ancestor (evolu­tionary hypoth­esis)
Orthology
homologous that have diverged after a speciation event
Paralogy
homologous that have diverged after a duplic­ation event
Xenology
homologous that derived through lateral transfer

Insects enviro­nments

1. Caves
2. Forests
3. Meadows
4. Deserts
5. Urban enviro­nments
6. Lakes and rivers
7. Agroec­osystem
Agroec­osystem → many species interact. They're natural ecosystem modified for the production of food and fiber
Planned diversity: plants and animals farmed + benefical organisms added
Unplanned diversity: weeds, pests, other organisms

Intera­ctions: demoec­ology

Demoec­ology
studies the demography of a population (density, structure, dynamics) and predicts future population in a given scenario
Metapo­pul­ation
when the indivi­duals live in a fragmented habitat
Structural properties
density, distri­bution, size, age classes, sex ratio, genetic variab­ility
Functional properties
behaviour, birth rate, mortality, genetic variab­ility

r vs k strategy

r:
1.expo­nential growth
2. short life cycle
3. small size
4. collapse dued to abiotic factors
5. related to ephemeral enviro­nments, can cause serious damage
6. large offspring, null parental care
k:
1. logistic growth
2. long life cycle
3. medium­-large size
4. rarely collapse because of abiotic factors
5. related to stable enviro­nments
6. reduced offspring, parental care

Multit­rophic intera­ctions

Green leaf volatiles
esters, aldehydes, alcohols C6
terpenoids C10, C15, indoles
These are volatiles induced by the insect injuries.

They:
1. have a repellent action
2. induce plant-­defence genes
3. attract other phytop­hagous (kairo­mones)
4. attract parasi­toids and predators (synom­ones)

Insects defense towards GLS

1. Detox of isothi­ocy­anates by conjug­ationo with Glutat­hione
2. Hydrolysis of GLS to obtain less toxic compounds (nitriles)
3. GLS seques­tration to use against predators

Symbiosis

Blockmann
observed Bacter­iocytes in the body fat cells of cockro­aches
Sulc
described aggreg­ations of bacter­iocytes in the body cavity of cicads

Endosy­mbiont

Primary
Obliged associ­ation, associated with their insect for long time, host-s­ymbiont coclad­oge­nesis, vertically transm­itted (ie roaches and blatta­bac­terium)
Secondary
Facult­ative symbiont, roles from mutualism to manipu­lation of reprod­uction, recently associated with their host
FUNCTIONS:
→ supplement of metabolic functions
→ manipu­lation of host reprod­uction
→ protection against pathogens or toxins

Manipu­lation of host reprod­uction

The heredi­tary, vertically transm­itted symbiont does:
help hosts that trasmit it OR sterilize hosts that don't trasmit it (kill male embryos, induce cytopl­asmatic incomp­ati­bility, feminize males, induce parthe­nog­enesis)
Wolbachia
kills male embryos, feminizes male, induces parthe­nog­enesis, induces cytopl­asmatic incomp­ati­bility (CI)
CI:
infected sperm + infected egg = ✓︁
infected sperm + healthy egg = X︁
healthy sperm + infected egg = ✓︁
healthy sperm + healthy egg = ✓︁

Insects species in Italy

Alloch­tonous
Aedes albopi­ctus, Trichopoda pennipes, Scapho­ideus titanus, Leptog­lossus occide­ntalis, Metcalfa pruinosa, Icerya purchasi, Halyom­orpha halys, Vespa velutina,
Others
Dros­o­phila suzuki, Diabrotica virgifera, Empoasca vitis, Lobesia botrana, Cysia ambigu­­ella, Argyro­­tenia pulche­­llana
 

Key points in evolution

1
Cambrian explosion
2
Origin of Insecta
3
Vascular plants
4
Seed plants
5
End-pe­rmiam mass extinction
6
Flowering plants
7
Angiosperm
Remember the Cambrian explosion thanks to Opabinia, the weirdest animal ever

Zoology - Arthropoda

arthron = articu­lated ; podos = foot
1.200.000 described species
Exoske­leton
Bilateria, protos­tomes and triplo­blastic
Metameric segmen­tation; tagma
High adapta­bility
Ectotherms

General Morphology

Hetero­nomous metamery: 20 metamers
Each metamer: ventral sternite, dorsal tergite, pleura (lateral sclerite), one pair of spiracle, one pair of ganglia, a couple of appendixes
3 morpho­logical regions (tagma) → Head (6 metamers fused), Thorax (3 regions: pro- meso- meta-), Abdomen (11 metamers or urites + telson)

Pterygota

Endopt­erygota
Neuroptera
Megalo­ptera
Raphid­ioptera
→Coleo­ptera
Streps­iptera
→Diptera
Mecoptera
Siphon­aptera
Tricho­ptera
→Lepid­optera
→Hymen­optera

DNA Taxonomy is useful because:

It's a standa­rdized approach to identi­fic­ation
Solves limita­tions of morpho­logical approaches
Identifies organisms also from fragments or juvenile stages
Solves the "­tax­onomic impedi­men­t"

Morpho­logical approach

Easy on the most cases
but what about fragments or juvenile stages?
Species:
groups of interb­reeding natural popula­tions that are reprod­uct­ively isolated from other such groups
The morpho­logical species concept:
Operat­ional tool of the biological species concept → the existence of reprod­uctive isolation is deduced by the analysis of morpho­logical traits
Cons:
Subjective (the specialist decides); Intras­pecific varabi­lity; Cryptic species

Applic­ation os DNA taxonomy

Outside entomology
Food safety
Inside entomology

Applic­ation of DNA taxonomy

Outside entomology
Food safety, veterinary applic­ation
Inside entomology
Forensic science, biomon­ito­ring, biodiv­ersity surveys, invest­igate multit­rophic relati­onships

DNA barcoding vs DNA Metaba­rcoding

DNA barcoding
sequences 1 DNA to identify 1 organism
DNA metaba­rcoding
sequences 105-107 DNA to identify organisms, simbionts, parasites, dead remnants and extrac­ellular DNA

Sequence

Definition: S, is an order of n characters (Si)
DNA is composed of 4 nucleo­tides (A, C, G, T)
RNA is composed of 4 nucleo­tides (A, C, G, U)
Proteins are composed of 20 aminoacids

Ecosystem

It's a structural and functional unit consisting of a biological community of living organisms intera­cting with themselves and their physical enviro­nment, in a unit of space
Ecological factor: every enviro­nmental element intera­cting directly on living organisms
Biotic factors: influence organisms' fitness and distri­bution

Sampling

Direct
qualit­ative, useful for presen­ce/­absence analyses, depends by the human experience
Indirect
quanti­tative, useful for hypotesis testing, do not depend by human

Intera­ctions: autoec­ology

Autoec­ology
Study of the indivi­duals: range of tolera­nces, thermo­reg­ula­tion, water balance
Autoec­ology studies guilds:
-Herbi­vores
- Predators
- Scavengers
- Parasites and parasi­toids

Trophic guilds

Scavengers
Feed on dead or dying plants, dead or dying animals, excrements of other animals
Phytop­hagous
phyllo­phagous (leaves), carpop­hagous (fruit), plant-­sucking (xylem, phloem), anthop­hagous (flowers), rhizop­hagous (roots), xyloph­agous (wood)
Zoophagous
feed on other animals (predators and parasi­toids)

Intera­ctions: Sinecology

It studies the intera­ctions among species in a definited space
Compet­ition, Predation, Symbiosis
Compet­ition is higher in a limited enviro­nment (ie leafmi­ners). It can be symmetric or asymmetric (if one species is more compet­itive than the other)
Predation: prays evolve features to defense, predators to overcome the preys strategies
Symbiosis: parasi­tism, mutualism, commen­salism

Detox of plant's defense compounds

1. reduction of toxicity by ctyochrome P450 monoox­yge­nases (CYPs). Heme-c­ont­aining enzimes catalyzing

2. hydrop­hobic compounds are converted in hydrop­hilic by Glutat­hione S-tran­sfe­rases (GSTs) and Uridine 5'-dip­hos­pho­-gl­ucu­ron­osy­ltr­ans­ferases (UGTs) catalysing the conjug­ation of GSH from uridine 5diP glucoronic acid to the xenobiotic substance

3. ATP binding cassette (ABC) transports xenobi­otics outside the cell

Damages caused by insects

Direct
Insect directly attacks the commercial parts
Indirect
Insect attacks non-co­mme­rcial parts but reduces plant efficiency
Physio­logical damage
Phyllo­phagous insects reduce leaves surface, reducing photos­ynt­hesys, of aphids can induce presence of black sooty mold or viruses, rhizop­hagous and xyloph­agous insects
Productive damage
measurable plant loss (quali­tative and quanti­tat­ive), or aesthetic damage
Economic damage
monetary value of the productive damage

Causes promoting pest damage

Abiotic factors
Biotic factors (plant genotype, insect prefer­ence, phenol­ogical phase)
Random factors

Relati­onships

/
Parasitic
Mutual­istic
Facult­ative
male killing, femini­sation
increase fecundity
Obligate
oogenesis
nutrient provis­ioining
Vertically transm­itted symbionts:
- reprod­uctive parasitism
- mutual­istic symbiosis
- standard parasitism

Open questions about symbiosis

Understand molecular basis of insect­-sy­mbiont intera­ctions
Microbiota and microbioma associate to non-model insects
Impact of commensal bacteria in niche coloni­zation
Impact of ecological determ­inants on the microbiota structure
 

Metadata

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  • Published: 24th September, 2021
  • Last Updated: 30th September, 2021

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