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Entomology > Insect Anatomy Part 2 > Flashcards

Insect Anatomy Part 2 Flashcards

1
Q

Thorax/mesosoma 3 distinct sections

A
  1. prothorax - pair of legs
  2. mesothorax - pair of legs & wings
  3. metathorax - pair of legs & wings

each segment of thorax has appendages

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2
Q

what are insect sclerites?

A

series of integumental plates connected by tough, elastic membrane
- Nota = upper, concave plates
- Pleura = lateral, convex plates
- Sterna = ventral sclerites

Pronotum Mesonotum Metanotum
Propleuron Mesopleuron Metapleuron
Prosternum Mesosternum Metasternum

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3
Q

Thorax specialisation - apocrita - Hymenoptera

A

small waist
bees, wasps, + ants - not sawflies

Mesosoma = 3 thoracic segments + 1st abdominal segment (propodeum)

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4
Q

what does thorax specialisation depend on?

A

variation depends on needs of species
e.g. Odonata - mesothorax = greatly enlarged

hemimetabolous adult/young insects each sections supports pair of legs

Larvae of holometabolous species may lack legs (apodous)

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5
Q

what are legs?

A

six jointed appendages w/ multitude of functions

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6
Q

Leg structure

A
  • 3 pairs of walking legs - 1 pair per thoracic segment
  • 6-segmented (coxa, trochanter, femur, tibia, tarsus, pretarsus)
  • tarsus = subdivided + typically 2-clawed pre tarsus
  • 2-segmented trochanter (only 1 = muscled) occurs in Odonata + some Hymenoptera, but 2nd trochanter actually appears part of femur
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7
Q

Coxa

A

most basal aspect of insect leg

articulates w/ sternites

joint between coxa + body wall may be monocondylic, dicondylic, or even more complicated

may articulate w/ any one of several small sclerites, w/ the pleura, and/or the sternum

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8
Q

Trochanter

A
  • small
  • serves as joint between coxa and femur
  • joint between coxa and trochanter = always dicondylic joint
  • motion restricted to forward and backward direction (vertical plane)
  • appearance of two trochanters in Odonata - part of femur
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9
Q

Femur

A
  • long + stouter than other segments
  • contains main muscles used in running, jumping, digging
  • joint between trochanter + femur = usually fairly firmly attached or with only small amount of movement possible
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10
Q

Tibia

A
  • long + offers extra flexibility
  • may, carry spurs for defence
  • joint between femur and tibia = dicondylic joint (similar to the coxo-trochanteral joint)
  • head often bent so shank can flex against femur
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11
Q

Tarsus

A
  • foot or contact surface of leg
  • most insects, subdivided into from 2-5 tarsomeres (never 5+)
  • tarsomeres not true segments as lack individual musculature (seen in other segments)
  • basal segment (basitarsus) has monocondylic articulation w/ tibia
  • rest of joints lack true articulatory structures - freely moveable in membranous joints
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12
Q

Pretarsus

A

consists of:
- median lobe = arolium
- pair tarsal claws = ungues

Diptera have no arolium, but:
- membranous pulvilli
- ungues
- middle empodium (spine-like or lobe-like)

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13
Q

Ariolium

A
  • medium lobe may be membranous or partly sclerotised
  • act using suction from large numbers of minute tubular hairs enabling insects to hold onto smooth substrates
  • none in Diptera except Tipulidae (crane flies)
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14
Q

Ungues

A

assist insect in holding onto substrate or prey

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15
Q

Pulvilli

A

Diptera, 2 pads beneath claws

often covered with fine setae to aid attachment to surfaces

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16
Q

Empodia

A

Diptera - spine or lobe-like process arising from unguitractor

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17
Q

Leg adaptations

A

huge variety to suit different life histories

larvae + adults likely to differ

form + function

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18
Q

Natatorial

A

adapted for swimming e.g. diving bugs, water beetles

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19
Q

fossorial

A

adapted for digging in soil e.g. mole cricket

20
Q

cursorial

A

adapted for running, e.g. ground beetles, cockroaches

21
Q

raptorial

A

grasping, stabbing forelegs armed w/ lethal spines for catching and holding prey, e.g. Praying mantis

22
Q

Saltatorial

A

large, muscular hind legs adapted for jumping, e.g. locusts, grasshoppers, fleas, froghoppers

23
Q

Where do female bee species collect pollen?

A

on hind tibia + basitarsi - often enlarged + covered in dense hair = pollen brush

24
Q

Where do females of social bumblebees collect pollen?

A

have a corbicula (pollen basket) - smooth shiny area surrounded by ring of long hair on hind tibia

25
Q

what are wings?

A
  • 2 fine membranes supported by series of sclerotised veins
  • only adult insects possess fully functional wings
  • small wing buds visible on exoskeleton of hemimetabolous insect larvae
  • most insects have 2 pairs of wings: forewings on the mesothorax, hindwings on the metathorax
26
Q

wing adaptations

A

variety of specialisation

small insects, veins may be absent or consist only of central midrib supporting series of fine hairs

increase or decrease in venation network

wing folding + use of colour

27
Q

Secondary wing loss

A
  • wings present in one sex (often the male); rarely, female is winged but male not
  • selectively lost in “workers” of social insects
  • wings may be produced only at particular times in life cycle
  • structure + colouration will often vary w/ morphs, e.g. aphids, migratory phases of locusts + polymorphic butterflies
28
Q

Wings at rest

A
  • held flat, or folded number of times along specific patterns
  • complex wing folding in some groups
  • typically = hindwings folded, but in few groups e.g. vespid wasps, it is forewings
  • evolution of insect wings not well understood
29
Q

3 main theories on origins of wings

A
  1. developed from paranotal lobes, extensions of thoracic terga, originally acting as parachutes
  2. wings derived from tracheated gills or gill covers
  3. from inner (endite) or outer (exite) leg segments close to body. fossil and molecular evidence
30
Q

Wing venation

A
  • characteristic network usually throughout the wing tissue
  • extensions of the circulatory system
  • filled w/ haemolymph & contain tracheal tube & nerve
  • in membranous wings, the veins provide strength + reinforcement during flight
  • venation can be used for taxonomic identification, e.g. Tipulidae (craneflies)
31
Q

wing functions (6)

A
  1. communication
  2. camouflage
  3. thermoregulation
  4. protection
  5. balance
  6. flight
32
Q
  1. communication
A

bright colours (incl UV) = wing patterns provide a means of inter- and intra- specific communication

33
Q
  1. camouflage
A

crypsis allows the insect to hide from its predators or helps it to surprise its prey

34
Q
  1. thermoregulation
A

different colours reflect/absorb different wavelengths of light

e.g. black patches on wing of some Alpine butterflies help absorb solar radiation

they can thermo-regulate by changing wing posture

35
Q
  1. protection
A
  • modified, hardened forewing of Coleoptera - elytra (sing. elytron) - hemelytra in Hemiptera
  • protect hindwings which are used for flying
  • elytra opened, hindwings extended
  • modified, leathery forewing of Orthoptera, Dermaptera, Mantodea, Phasmatodea + Blattodea = tegmina (sing. tegmen)
36
Q
  1. protection - role of tegmina
A

protecting hind wings when folded

important in camouflage + displays

e.g. defensive display - tegmina drab, but cover aposematic displays that are startling when uncovered

e.g. hardened Coleoptera elytra, Hemiptera hemelytra, + Blattodea tegmina

37
Q
  1. Balance
A
  • hind wings of Diptera modified into halteres that vary in size + concerned w/ stability in flight
  • basal lobes of halteres have companiform sensilla
38
Q

Flight evolution

A
  • escape predators, find food + habitats
  • only invertebrates that can fly
  • acquired ability ~ 300 MYA
  • effective - escape from predators, transportation
  • allows movement to new habitats + resources
39
Q

Flight muscles

A
  • influence wing beat + refers to muscle attachments relative to wing
  • muscle attachment can be direct or indirect
40
Q

Direct flight muscles

A
  • wing muscles insert directly at wing bases, which are hinged
  • small movement of wing base downward lifts wing itself upward
  • found in Paleoptera, i.e. Odonata + Ephemeroptera
41
Q

indirect flight muscles

A
  • muscles attached to thorax - flight powered by force of muscle contraction + distortion of thorax
  • dorsal longitudinal muscles compress thorax causing dorsal surface of thorax (notum) to bow upward, making wings flip down
  • Tergosternal muscles pull notum downward again, causing the wings to flip upward
  • associated w/ wing-folding mechanism of Neoptera and is a defining feature of this group
42
Q

Synchronous and asynchronous contraction

A

refers to ratio of muscle contraction relative to nervous innervation

affects wing beat and wing beat frequency

43
Q

Synchronous contraction

A
  • conventional 1:1 relationship between nerve impulses + contraction
  • used for wing frequencies up to 100 Hz
  • present in less advanced groups of insects: Odonata, Blattodea, Orthoptera, Lepidoptera
44
Q

Asynchronous contraction

A
  • allows for more rapid contraction + higher wing beats, i.e. wing-beat frequencies > 500 Hz
  • present in more advanced groups of insects: Hymenoptera, Coleoptera, Diptera, Hemiptera
45
Q

Beat frequencies
- is direct or indirect muscles more efficient?

A

indirect muscles are more efficient and capable of higher wing beat frequency

Odonata - direct muscle attachment, synchronous - low beats per second (20-26/sec, 25 km/hr)

Diptera - indirect, asynchronous - high beats per second - balance - how fly fast? - one pair of wings, lost wings to fly faster (300-550 beats/sec, 32 km/hr)

Hymenoptera - indirect, asynchronous - high beats per second - join front and back wings w/ little hooks called hamuli (200 beats/sec, 22 km/hr)

Entomology (12 decks)

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