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Entomology Flashcards

1
Q

What are the primary functions of the Mandible and Maxillae?

A 
Mandible: 
cut, tear, crush, chew
provide defence
cutting edge & grinding molar area 
extremely hard
Maxillae:
lacinae: hold and macerate food
galea & palps: bear sensory setae & chemoreceptors to test food before ingestion
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2
Q

b) Describe the difference between haustellate and mandibulate mouthparts.

A 
Haustellate: 
used by lepidoptera & some flies
forms a probiscis to suck liquid
liquid is pumped by ciborium and/or pharynx muscles
Mandibulate: 
used by omnivores
used for chewing and biting
5 components: 1) labrum, 2) hypopharynx, 3) mandible, 4) maxillae, 5) labium
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3
Q

c) What role does the cuticle play in the external anatomy of the insect?

A
  • surrounds & protects: body, limbs, apodemes, wings
  • along with epidermis it forms the integument
  • regulates water loss
  • enables colouration
  • deters predators
  • enables mimicry
  • provides camouflage
  • gives olfactory cues
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4
Q

d) What advantages did the development of wings / flight provide?

A 
orientation
dispersal
access to a variety of environments for exploitation (eg. plant microhabitats/foliage)
evasion of predators
protection
finding a mate
visual communication
sound production
heat retention
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5
Q

Outline the four main functions of haemocytes (blood cells) in insects.

A
  • phagocytosis - the ingestion of small particles and substances like metabolites
  • haemolymph coagulation - stops bleeding of wounds
  • encapsulation - of parasites & other large foreign materials
  • storage & distribution of nutrients
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6
Q

c) What are the 3 main regions of the insect gut and what are the functions of each section?

A 
1) Foregut (has cuticular lining): 
ingestion
storage
grinding
transport of food to next region
2) Midgut (no cuticular lining):
digestive enzymes produced & excreted
absorption of digested products
transport of material remaining in the gut lumen & urine from Malpighian tubules to next region
3) Hindgut (has cuticular lining):
absorption of water, salts and other molecules
transport of waste material to rectum for expulsion
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7
Q

d) What role does the thracheal system play in insect life?

A 
uptake of oxygen
expulsion of carbon dioxide
invaginations of the epidermis
continuous with the body cuticle
air enters system via spiracles (spiracles include an air chamber atrium & opening/closing valve)
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8
Q

What is bioluminescence and what is it used for?

A

biochemical emission of light by living organisms
achieved by the enzyme luciferase oxidising with luciferin in the presence of ATP & oxygen, which produces light. pH differences vary light colour.
Used for:
signalling courtship
warning distastefulness
luring prey

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9
Q

b) How do Orthopterans produce and amplify sound?

A

Stridulation:
the scraper is rubbed against the file, causing a vibration
the scraper is a ridged or plectrum-like
the file is a series of teeth, ridges or pegs
the file makes little noise, so it is amplified via tegmina (modified fore wings)

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10
Q

c) Explain the importance of acoustic communication to insect ecology and behaviour and outline the main way close range vibration signals are received.

A

Importance:
courtship (eg. orthopteran males producing ‘songs’ from which females base mate choice
detection of predators
Received:
Non-tympanal reception (2 types)
substrate-borne signals
large translational movements of surrounding medium (air or water) that occur close to sound. This is detected by either sensory hairs or specialised sensory organs.

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11
Q

d) What are the four ways that insects can detect light? Briefly name and describe the four ways insects can detect light.

A

1) Compound Eyes:
most sophisticated
comprised of many individual ommatidia, which together provide 360 degrees vision
each ommatidium resembles a simple stemma: has cuticular lens overlying a crystalline cone which directs & focuses light onto 6-10 retinal cells
2) Stemmata:
organs located on head
has a cuticular lens overlying a crystalline body
light is focused via the lens onto a rhabdom
each stemma points to a different direction so insect only sees a few points in space
3) Dermal Detection:
light detection through body surface
sensory receptors below cuticle
4) Ocelli:
typically, 3 are arranged in a triangle on top of head
covered by a transparent cuticle that may be curved as a lens, that covers transparent epidermal cells so that light passes through to a retina
this retina is comprised of rhabdoms so that a blurred image is received

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12
Q

What are the three different ways in which a male insect may provide food to a female before, during or after copulation?

A

1) collected, captured or regurgitated food
2) attractive chemicals from a glandular product (including the spermatophore)
3) being consumed by female (cannibalism)

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13
Q

b) There are two main types of sexually selected adaptations in males that increase certainty of paternity, what are they?

A

1) Displacing the ejaculate of other males that female mated with previously
2) Reducing occurrence/effectiveness of inseminations by other males after mating:
mating plugs
male-derived secretions that switch off female receptivity
prolonged copulation
guarding females
structures for gripping female during copulation

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14
Q

c) What is sperm competition and what are some of the influences that effect which sperm is used for fertilisation

A
  • when sperm from two or more males compete to fertilise the eggs
  • physiological (events inside female reproductive tract) & behavioural (mating behaviour) mechanisms determine outcome of sperm competition
  • high copulation = low time investment per copulation = low certainty of paternity VS low copulation = high time investment per copulation = high certainty of paternity
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15
Q

Identify and describe the three forms of development in insects.

A

Embryonic - begins as soon as the female deposits the egg.

Larval/Nymph - marks the beginning of the first stadium, when the insect is in its first instar. This stage ends at the first ecdysis, when the old cuticle is cast to reveal the insect in its second instar.

Adult - The adult stage has a reproductive role, and is often the dispersive stage in insects with relatively sedentary larvae.

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16
Q

List the three main hormones involved in moulting and metamorphosis of insects and briefly describe the role of each.

A

1) Neuropeptides - (prothoracicotropic hormone (PTTH), ecdysis-triggering hormones (PETH, ETH) and eclosion hormone (EH) - regulates most aspects of development, metabolism, homeostasis and reproduction
2) Ecdysteroids - a steroid hormone that promotes moulting
3) Juvenile hormone (JH) - signalling hormone: modifies the expression of a moult, regulates metamorphosis & reproduction

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17
Q

Explain the process that an insect needs to undergo in order to grow.

A
  • intermittent phases called ‘stadiums’
    stadiums are periods between moults
  • a moult is when a new cuticle of increased surface area is formed
  • moulting include apolysis (separation of the cuticle from the epidermis) and subsequently ecdysis (shedding of the old cuticle)
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18
Q

Compare and contrast diapause and quiescence? Give an example of an Orders/ Families that exhibit each.

A
  • Diapause: the suspension of development in response to a predetermined lifecycle stage (obligatory) or environmental cues (faculative) - eg. day length. Development recommences following certain physiological stimuli. FAMILY: Nymphalidae
  • Quiescence: the slowed/halted development in response to unfavourable conditions - eg. extreme cold. Development recommences once favourable conditions return. FAMILY: Pulicidae
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19
Q

Define what characterises the Pterygote subclass and describe the divisions within this subclass.

A
  • winged or secondarily wingless (apterous)
  • thoracic segments of adults large
  • meso- and metathorax united to form pterothorax, bearing wings
  • lateral regions of thorax well developed
  • 11 or fewer abdominal segments
  • lack styles and vesicular appendages found on apterygote insects
  • spiracles primarily have a muscular closing apparatus
  • mating is by copulation
  • metamorphosis is hemi- to holometabolous
    Divisions:
  • Palaeoptera: “old wings” - wings cannot be folded against abdomen at rest (because wing articulation with the thorax is via axillary plates that are fused with veins. This condition is termed “palaeopteran” or “palaeopterous”)
  • Neoptera: “new wings” - wings capable of folding back against abdomen at rest (wing articulation derives from separate movable sclerites in the wing base, and wing venation has none to few triadic veins, and mostly lacking anastomosing (joining) cross-veins)
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20
Q

Briefly describe the diagnostic characteristics of the Neoptera and list three examples of orders that belong to this division.

A
  • wings capable of folding back against abdomen at rest
  • wing articulation derives from separate movable sclerites in the wing base
  • wing venation with none to few triadic veins, and mostly lacking anastomosing (joining) cross-vein
  • Orders: Plecoptera (stoneflies), Dermaptera (earwigs), Orthoptera (grasshoppers, locusts, katydids andcrickets)
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21
Q

What are the key differences between palaeopteran and neopteran insects?

A
  • Palaeoptera: wings cannot be folded against the abdomen at rest. Wing articulation with the thorax is via axillary plates that are fused with veins.
  • Neoptera: wings can fold back against the abdomen at rest. Wing articulation derives from separate movable sclerites in the wingbase. Wing venation with none to few triadic veins. Mostly lacking anastomosing cross-veins.
22
Q

What are the diagnostic features of hexapoda?

A
  • unique tagmosis - specialisation of successive body segments that unite to form sections or magmata (namely the head, thorax and abdomen)
  • head is composed of a pregnathal region and three gnathal segments bearing mandibles, maxillae and labium
  • eyes are variously developed and may be lacking
  • thorax comprises three segments, each of which bears one pair of legs,
    thoracic legs have 6 segments max
    if abdominal limbs present, they are smaller and weaker than those on the thorax
23
Q

List and detail the four possible routes that flight in insects may have evolved.

A

1) Floating: small insects assisted in passive dispersal
2) Paragliding: winglets assisted in stable gliding or parachuting from trees/tall vegetation, perhaps after a powered leap
3) Running to jumping to flying
4) Surface sailing: raised winglets allowed adults of aquatic insects to skim across water

24
Q

Why do contemporary insects no longer exhibit gigantism?

A
  • modern oxygen levels reduced compared to Carboniferous & Permian periods
  • gigantic flying insects in a modern atmosphere would require such dense tracheae to be airborne that there wouldn’t be space for muscles/organs
  • increasing numbers of flying vertebrate predators (birds/bats) likely competed with gigantic insects for food
25
Q

Discuss the evidence for the terrestrial origins of the insects.

A
  • all early nodes in hexapod phylogenetic tree are best estimated as being terrestrial & no fossils to suggest otherwise
  • difficult to imagine how a tracheal system could have evolved in water (in air, invagination of external respiratory surfaces & subsequent internal elaboration likely gave rise to tracheal system that later served as a preadaptation for tracheal gas exchange in the gills of aquatic insects)
26
Q

Explain how the megadiversity of the Holometabola can be attributed to their metamorphosis.

A
  • larval juvenile instars highly differentiated from adults
  • as larvae different, they have different resource requirements & do not compete for resources with the adults (whereas hemimetabolans share the same lifestyles typically)
  • this separation of resources allowed them to evolve to occupy varying habitat niches between larval & adults stages, subsequently leading to increased diversity
27
Q

Describe the importance of introduced dung beetles to Australian Agriculture.

A
  • no native ungulates, so no native dung beetles
  • introduced dung beetles reduced the negative impacts of feces from cattle, sheep and horses by burying it
  • pasture quality improved and the over-population of flies reduced, thus improving Australian agriculture
28
Q

Outline the different feeding types of ground-dwelling insects.

A 
Root-feeding insects
Dead trees or decaying wood
Fungus eating
Dung feeding
Carrion eating
Stream derived plant debris in caves
29
Q

Soil dwelling insects show distinctive morphological variations due to their lifestyle, what are some examples of these adaptions? And in what Orders/ Families are they found?

A

Adaptations:
- larvae have well-developed legs
reduced eyes
- hardened forewings or wings reduced, shed after dispersal, or lost altogether
- pupae frequently have spines - transverse bands
Orders/Families:
mites (Acari)
termites (Termitoidae)
ants (Formicidae)
many beetles (Coleoptera)
immature stages of flies (Diptera) and moths (Lepidoptera), may also be abundant

30
Q

Insects that live in the soil are more susceptible to infection of fungi and bacteria due to the conditions they live in. How do they protect themselves?

A
  • Antibacterial properties: many ground-nesting ants protect themselves with antibiotic secretions from the metapleural glands on the thorax
  • Antimicrobial properties: many earwigs protect themselves with antimicrobial secretions from the abdomen
31
Q

Why are there so few marine insects?

A
  • Crustacea and Mollusca evolved before insects & thus dominated the marine environment first, leaving few niches for insects to adapt to
  • flight and internal fertilisation are unnecessary in a marine environment, as gametes may be deposited directly into water and dispersed via currents
32
Q

Briefly describe how insects exchange gas within aquatic environments.

A
  • Eggs:
    absorb oxygen via a chorion (expanded in some species with horns or crowns, or have increased efficiency due to parental assistance
  • Small species:
    gaseous exchange via the cuticle suffices
  • Large species:
    additional mechanisms are required
    gills (some of which may store air pockets)
    respiratory pigments
    respiratory organ to pierce the roots and stems of aquatic macrophytes which hold air
    ability to suspend from water meniscus
    positioning in areas of high water velocity
33
Q

Outline some adaptations aquatic insects have to lentic (still) and lotic (flowing) environments.

A 
Lentic:
hair piles on legs
discharge of a chemical to move over water surface
diurnal vertical migration
ability to actively swim/dive
Lotic:
being torso-ventrally flattened
seeking rock crevices and plant matter clumps (eg. leaves)
burrowing into substrate
allowing drifting with the water
34
Q

In what ways do insects assist in plant reproduction and dispersal?

A
  • Insect pollination (entomophily):
    insect may visit flowers to collect nectar and/or pollen
    predatory insects may also pollinate flowers just by landing on flower
    insects may try to mate with the flower if it resembles a female
  • The plant is fertilised by the pollen from another plant that the insect has visited.
35
Q

Describe the structural differences between a domatia and a gall.

A
  • Domatia (little houses):
    hollow stems
    tubers
    swollen petioles or thorns
    used by ants and other insects for feeding and/or nest sites
  • Galls (pathologically developed cells):
    tissues or organs of plants that have arisen by hypertrophy (increase in cell size) and/or hyperplasia (increase in cell number) as a result of stimulation from foreign organisms
    mostly induced by insects - but also viruses, bacteria, fungi, nematodes and mites
36
Q

Define Entomophily. List some of the advantages disadvantages of using this pollination mechanism.

A

Entomophily:
insect pollination
Advantages:
- increase in pollination efficiency
including reduction in pollen wastage
- successful pollination under conditions unsuitable for wind pollination
- maximisation of the number of plant species in a given area (eve rare plants can receive conspecific pollen carried into the area by insects)

Disadvantages:
plants rely heavily on the presence of insects in order to reproduce - if the insects are not presence or if their lifecycles alter (eg. due to climate change) this could have detrimental effects on the plant

37
Q

What is xylophagy? Identify one type of xylophagous insect and describe how it eats.

A
  • Xylophagy: the habit of solely or primarily eating wood
  • Insects:
    Termites
    termites use either symbiotic flagellates in their hind-gut, or they produce celluloses to break down dead or living wood (with the exception of Macrotermitina, which uses fungi to pre-digest wood)
38
Q

Describe some of the nesting behaviours used by Termites

A

There are 4 broad nesting categories:

1) nesting and eating in a single piece of wood or several closely associated species
2) starting in a single piece of wood but searching for and eating other pieces and moving the nest to another piece once the first is eaten
3) nesting separately from the food (not necessarily wood) and foraging to locate food
4) continuously mobile with no permanent nest, as in soil feeders that consume decomposed plant material

39
Q

What are the traits that define eusociality? Provide examples of insects that exhibit this type of social behaviour.

A
  • Traits:
    Division of labour with a caste system involving non-reproductive individuals assisting those that can reproduce
    Cooperation amongst colony members when tending to young
    Overlapping of generations
  • Example:
    all ants and termites, and some bees and wasps (eg. vespine paper wasp)
40
Q

Why do most parasitoids host discriminate?

A
  • avoids hosts that are already parasitised (by themselves, their same species, or another species)
  • distinguishing hosts generally involves marking the host by placing a pheromone internally or externally at the time of oviposition
41
Q

What are some of the strategies that parasitoids employ to overcome host immune responses?

A

Avoidance:

  • feeding externally on host (as opposed to internally)
  • egg parasitoids lay into host eggs that may have no/weak immune response
  • occupy host organs (eg. brain)
  • escape immune reaction of host

Evasion:

  • molecular mimicry (coated with a substance similar to host proteins and is non recognised as non-self by the host)
  • cloaking by insulating itself in a membrane or capsule
  • rapid development within the host

Destruction:
- host immune system blocked by attrition of the host such as by gross feeding that weakens host defence reactions and/or destruction of responding cells

Suppression:

  • host cellular immune responses suppressed by viruses associated with the parasitoids
  • often accompanied by reduction in host haemocyte counts

Subversion:
- parasitoid development occurs despite host response

42
Q

What is hyperparasitism? Provide examples of insect orders that contain hyperparasitoid families.

A
  • a secondary parasitoid develops at the expense of a primary parasitoid
  • obligate (develop only within primary parasitoids)
  • facultative (may develop also as primary parasitoids)
  • Orders: Diptera, Coleoptera, Hymenoptera
43
Q

Compare and contrast Batesian mimicry and Müllerian mimicry.

A

Batesian:
a palatable species obtains protection from predation by resembling an unpalatable species

Müllerian:
two or more unpalatable species obtain protection from predation by resembling each other

Both strategies warn predators away - but Batesian is beneficial to the palatable species only and is entirely an false warning, whilst Müllerian is beneficial to multiple unpalatable species and is a true warning

44
Q

What methods do insects use to defend themselves from predators?

A

Hiding: Eg. Crypsis - resembling a uniform coloured or patterned background, being countershaded – light below and dark above, having a pattern to disrupt the outline, having a bizarre shape to disrupt the silhouette. Or Eg. Mimesis - resembling an object that is a particular specific feature of its environment, but is of no inherent interest to a predator, such as a bird dropping.

Thanatosis - Feigning death.

Startle display - Eg. opening the forewings and reveal brightly coloured “eyes” that are usually concealed on the hind wings.

Convergent appearance of part of a vertebrate. Eg. Alligator bug

Mechanical defences - Eg. lateral compression of flea to be difficult to dislodge, spiny legs & modified mouthparts, a heavily sclerotised cuticle, construction of a defence that doesn’t appear to contain an insect such as caddisfly, waxes and powders secreted to entangle mouthparts of predators.

Chemical defence - a chemical may repel a predator but alert conspecific insects to the predator’s presence and may act as a stimulus to move into action.

Mimicry - (Batesian - an aposematic inedible model has an edible mimic), (Müllerian - the model(s) and mimic(s) are all distasteful and warningly coloured, and all benefit from coexistence, as observers learn from tasting any individual).

Collective defence in gregarious and social insects. Eg. termites, clusters of b

45
Q

What are the six key aspects of malarial epidemiology disease transmission – why is each important?

A
  1. Vector distribution - determines the varying spread of malaria.
  2. Vector abundance - Determines how many available vectors there are to transmit malaria.
  3. Vector survival rate - If a mosquito dies within eight/nine days of initial infected blood meal, no sporozoites will become available & no malaria is transmitted.
  4. Anthropophily of the vector - In strongly anthropophilic vectors, transmission is high as the disease carrying vector will likely feed again on another human. In low anthropophilic vectors, transmission is lower, as the vector can also feed on non-humans.
  5. Feeding interval - a shorter interval = more feeds = increased likelihood of multiple hosts becoming infected
  6. Vector competence - An uninfected mosquito may not become infected when feeding on a host, the parasite may fail to replicate in the vector, or the mosquito may fail to transmit the parasite.
46
Q

b) What are the four key corpse physical feature stages in Forensic Entomology. How is each stage characterised, and what insects are most commonly found at each stage?

A

1) Putrefaction (normal/swollen by gases - days 1-14). Blow flies & house flies.
2) Black putrefaction (swollen by gases/flat, flesh creamy - days 11-20). Cheese-skipper larvae & skin beetles.
3) Butyric fermentation (flat, flesh creamy/drying out - day 18-3rd month). Larvae of fruit flies and a hover fly (the rat tailed maggot).
4) Dry decay (flat, drying out/hair and bones only - day 30-12th month). Skin beetles & clothes moth.

47
Q

What are the seven key methods used in Integrated Pest Management? Make brief notes on each method.

A

1) Chemical Control - enter the insect body via the cuticle, inhalation into tracheal system, or oral ingestion.
2) Biological Control - human intervention to restore biological interactions by introducing or enhancing the natural enemies of target organisms (eg. insect pests or weedy plants)
3) Host-plant Resistance - inherited genetic qualities that result in one plant being less damaged than another. The 3 categories of plant resistance are: 1) antibiosis, 2) antixenosis, 3) tolerance.
4) Physical Control - non-chemical, non-biological methods that destroy pests or make the environment unsuitable for the entry or survival of pests. Passive (e.g. fences, trenches, traps, oils and inert dusts) or active (e.g. mechanical, impact and thermal treatments).
5) Cultural Control - reducing insect populations in crops Eg. timing or placement of plantings to avoid synchrony with pests
6) Pheromones and Other Insect Attractants - can misdirect the behaviour and prevent reproduction
7) Genetic Mutilation - introducing a heritable element into the target pest population via genetically modified members of the same pest species.

48
Q

In what ways may climate change affect economically important insects and their roles in disease transmission?

A

Increased temperatures and altered rainfall patterns lead to regions becoming newly suitable for more tropical and subtropical vectors.

The arrival of exotic diseases is enhanced by many of our activities, including migration of humans infected with pathogens. Eg. Malaria

49
Q

In what ways may climate change affect economically important insects and their roles in crop production?

A

pest insects may grow out of control and decimate crops. Eg. insect hosts may become less vulnerable to parasitism due to warmer conditions.

potential earlier emergence of adults and eggs being laid earlier and thus, will miss the season during which they would normally become parasitised.

crop plants may escape pest insects if the insects are more vulnerable to climate change.

50
Q

b) What are the major regions of the central nervous system (CNS)? How does the CNS structure differ among different taxa?

A

Consists of series of ganglia joined by paired longitudinal nerve cords called connectives.

Regions:

  • Ventral nerve chord: Chain of thoracic and abdominal ganglia found on the floor of the body cavity
  • Brain has three pairs of fused ganglia = protocerebrum, deutocerebrum, tritocerebrum.
  • Suboesophageal ganglion has coalesced ganglia (of the three mouthpart-bearing segments (mandibular, maxillary and labial) with nerves emerging that innervate the mouthparts

Differs among taxa by:
- Varying degrees of ganglia fusion.

Entomology (1 decks)

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