Insects Flashcards
(115 cards)
1
Q
What defines an insect?
A
- 6 legs at some point in their life (some exceptions)
- Body divided into 3 tagma (head, thorax & abdomen)
- 1 pair of antennae
- All winged inverts are insects
- not all insects have wings
2
Q
Why are insect herbivore - plant interactions important
A
- Nutrient recycling
- Crop yield
- Community structure
- Biodiversity
3
Q
First insect fossil
A
-
Palaeodictyoptera
Found in the carboniferous - Modern mayflies and dragon and damselflies resemble
4
Q
Where did insects come from? Arthropod origin theories?
A
Solution 1: Arthropods have several origins?
Solution 2: Arthropods have a single origin?
5
Q
Solution 1: Arthropods have several origins?
A
- Sidnie Manton → similarities in arhtropods were due to constraints imposed by a rigid exoskeleton.
- Differences in the limb morphology
- Uniramous / biramous
- Uniramia hypothesis
- Convergence of several traits associated with the shift to land
6
Q
Solution 2: Arthropods have a single origin?
A
- Group called the ‘Cladists’ - believe that similarities in the arthropods are the best traits to use (Monophyly).
- Pan crustacea hypothesis
7
Q
Which gene gave evidence for how arthropods and insects arose?
A
- Brain and nervous system of arthropods is closer to crustacea than worms
- Developmental genetics distal-less gene - determines limb branching
- Insects and crustacea have same gene but is regulated differently
- Second hypothesis is now widely accepted
Zero marine insects and very few terrestrial crustacea
8
Q
So what gave rise to insects ?
A
Most likely a crustacean
9
Q
How insects are adapted for terrestrial life: Transitional habitats
A
bridging habitats
- Estuary
- Marsh
- Intertidal zone
- Mangroves
All slightly saline
10
Q
The challenges of terrestrial habitats and how insects overcame them.
A
- Water loss (probably solved by cuticle) - epicuticle
- Integument - living structure with production of wax
- Balance of electrolytes solved with malpighian tubules
- Respiration - not sure how this evolved - trachea (relatively unique). Spiracles
11
Q
The insect integument
A
The integument is the outer layer of the insect, comprising the epidermis and the cuticle
- Chitin based
- Extensive sclerotization
- Tough / flexible
Differs from crustacea
- no calcite
- more extensive protein x-links
- waxy epicuticle
12
Q
What makes the insect integument interesting?
A
- It is a living structure
- Wax on outer layer is continuously being refreshed
13
Q
Aquatic insects
A
- Aquatic insects have had to come up with workarounds for the trachael system.
E.g. Moquito larvae:
- The larva lives in water but breathes air through a siphon that penetrates the water surface, or, in some species pierces the roots of aquatic plants such as cattails.
14
Q
Synampomorphies
A
Shared Traits
15
Q
How are insects adapted to the increased impact of gravity in terrestrial habitats?
A
- Have a stable gait - move alternative legs, 2 legs on one side to 1 leg on the other (tripod gate) 3 legs always touching ground
- Small body size because of this
16
Q
Challenges to life on land?
A
- Respiration
- Water loss
- Support/movement/gravity
- Fertilisation
17
Q
Synapomorphy
A
- Character shared by all the descendent species
- Strong evidence for relatedness
18
Q
Synapomorphies of the Hexapoda (aka what makes an insect)
A
- Reduction of body segments. Pattern of tagmosiss: 6 segmented head, 3 segmented thorax, 11 segmented abdomen.
- Reduction in leg segments (fusion of the patella and tibia)
- Two primary pigment cells of the ommatidia.
- 9+9+2 pattern of microtubules in sperm flagellum
19
Q
Apterygota
A
Wingless insects
20
Q
Pterygota
A
Winged insects
21
Q
How to group basal insect lineages?
A
Two ways of grouping
1. Arrangements of the mouth parts
2. Or if they have wings or not
22
Q
Entognatha features
e.g.springtails
Lineages within Apterygota
A
- Enclosed mouth parts
- Virtually all have eversible vesicles of some kind (organs than can be turned out of the body
- Very small
- Underdeveloped malpighian tubules
- Reduced or absent compound eyes
23
Q
Entognatha species
Lineages within Apterygota
A
- Collembola (springtails),
- Diplura (bristletails),
- Protura
24
Q
Zygentoma
Lineages within Apterygota
A
Silverfish and Firebrats
25
Protura order
## Footnote
(within Entognatha)
* Simplest insect
* Antennae lost
* Eyes absent
* Elongated body
26
Oder Diplura
## Footnote
(within Entognatha)
* Simple oceli (no compound eye)
* Antennae
* Wingless
* Two prominent cerci (long tails)
27
Order collembola (springtails)
## Footnote
(within Entognatha)
* Fuculum (forked abdominal spring tail folded)
* Compound eye
* Antennae
* Wingless
* Collophore - Electrolyte balance, water uptake, adhering to surfaces etc.
28
3 innovations that spurred insect diversity
1. Evolution of wings
2. Evolution of wing folding mechanisms
3. Holometabolism(metamorphosis)
29
How did the variety of wings arise?
Two debated origins
## Footnote
Evolution of wings: Pterygota
**Paranotal hypothesis**
* Wings arose out of thorax (outgrowth)
**Pleural hypothesis**
* Gills that gave rise to wings
* Gene responsible for suppressing wing formations found in crustaceans
30
How did the variety of wings arise?
Two debated origins
| Which is correct?
* Still much debate, possibly a mixture of both?
* Duel-origin: Wings are derived from selective regulation of HOX genes in tissue from the **thorax** and the **pleural zones**
31
What was the intermediate function of wings? (how/why did they evolve)
* Courtship
* Thermoregulation - flap to cool
* Aerodynamics
* Respiration
* Possible evolved as a water surface skimming function
32
what is the indirect form of flight power in insects?
* Most insects dont directly use muscles to power flight
* **Insect pterothorax**
* Flight is powered by contorting thorax using dorso-longitudinal muscles and dorsoventral muscles.
* This causes the **notal hinge** to snap open or shut.
33
Paleoptera:
* Basal lineages,
* Unable to fold wings back over body
* No olfactory bulb in the brain
34
Mayflies
## Footnote
Paleoptera → Ephemeroptera
* 2500 species
* Aquatic with elaborate gills
* Greatly reduced hindwings
* Important prey item as they emerge on mass
* Emergence attuned to temperature
* Very threatened by climate change
35
what are Odonata?
## Footnote
Paleoptera → Ephemeroptera
Dragonflies and damselflies
36
Odonata synapomorphies
* Large compound eyes for predation
* Internal fertilisation
* Modified jaws of larvae
* Rectal gills – dense tracheae system, water drawn in muscularly
* Caudal gills (external)
* jet propulsion
37
Odonata eyes and brain
* No optical nerve insects
* Ommatidium
* Different sections of the ommatidium have different pigments
38
Odonata Copulation
* All male winged insects have a **aedeagus** - derived from a paired appendages on the 9th segment of the abdomen
* Scooping out sperm of other males
* Have secondary genitalia
39
Neoptera
* **Ability to fold wings**
* indirect flight muscles
* Monophyletic group
40
Postembryonic development
* **Ametabolous** - only relevant in apterygota
* **Hemimetabolous**
* **Holometabolous**
41
The Egg
| Life-cycles and Development
* Eggs differ between species
* Some lay live young (aphids)
42
Postembryonic development: **Ametabalous**
| Life-cycles and Development
* Only relevent in apterygota (wingless insects)
* Series of moults from egg to adult which allow growth
* Gradual change in body size but body form stays the same
43
Postembryonic development: **Hemimetabolous** development
| Life-cycles and Development
* Adult form has fully formed wings
* Distinction between adult and nymph
E.g. crickets / nymphs
44
Postembryonic development: **Holometabolous** development
| Life-cycles and Development
* Ecology of adults differs largely from larvae
E.g. Butterflies & Moths
* Non-feeding stage called a pupa between immature larva and adult
* Adult structures develop as imaginal discs inside larva
45
Nomenclature
| Life-cycles and Development
* Sets of stages (moults ect) are called **instars**
* Different insects have different numbers of instars
* Penultimate instar **subimago**
* Final instar - **imago**
46
Instar variation
| Life-cycles and Development
* Instar variation - some have 30+ some 5, some 4 etc
* Some species have fixed number of instar
* Some species can add an extra instar if they haven't got enough nutrients
47
Groups within Hemimetabola
| Hemimetabola. Basal neoptera (basal winged insects)
* Stoneflys (Plecoptera)
* Stick insects (Phasmatodea)
* Grasshoppers & Crickets (Orthoptera)
* Mantises (Mantodea)
* Cockroaches (Blattodea)
* Termites (Isoptera)???
* Thrips (Thysanoptera)
* True bugs (Hemiptera)
* Aphids, white flys.. (Sternorrhyncha)
* Cicadas.. (Auchenorrhyncha)
48
Stoneflys (Plecoptera)
| Hemimetabola. Basal neoptera (basal winged insects)
* Reduced ovipositor
* Accessory heart (pulsatile organ) associated with cerci
* 3-segmented tarsi
* High O2 requirement
* Adapted for aquatic life
49
Stick insects (Phasmatodea)
| Hemimetabola. Basal neoptera (basal winged insects)
* All herbivores
* Example of **crypsis** (mimic sticks - appearance and behaviour)
* Claspers present in males
50
Grasshoppers and crickets (**Orthoptera**)
| Hemimetabola. Basal neoptera (basal winged insects)
* **Cryptopleuron** (lateral extension of the pronotum)
* **Saltorial hindlegs** (jumping)
* Wings inclined over abdomen at rest (folding wing mechanism)
51
Mantises (Mantodea)
| Hemimetabola. Basal neoptera (basal winged insects)
* Enlarges raptorial forelegs
* Femoral brush on front leg
* Extraordinary head mobility
* Ootheca (egg mass) embedded in protective froth
Common features
* Camouflage and mimicry
* Cyclopean metasternal ear
52
Cockroaches (blattodea)
| Hemimetabola. Basal neoptera (basal winged insects)
* Wrap around eyes
* Dorsoventral flattened
* Slightly hardened, leathery (coreacious) front wings
Maternal and biparental care
* Adults protect nymphs
* Extended maternal care
* Retention of the ootheca (egg sac) (may be first step towards parental care)
53
Termites (Isoptera) < no longer an order - Evolved from cockroaches.
| Hemimetabola. Basal neoptera (basal winged insects)
* Evolved **eusociality** (different roles in colonies)
* No specific synapomorphies for termites
Termite mounds - thermoregulation
* Chimneys and tubes which drag air up from the colony - improves air flow
* Evenly distributed as as they compete for resources (evenly distributed colonies)
* Increase nitrogen levels around mounds- linked with even distribution of plant growth
54
Thrips (Thysanoptera)
| Hemimetabola. Basal neoptera (basal winged insects)
* Frilled wings (setae)
* Right mandible reduced - left mandible inflexible
* Pre-adult instar -
* Haplodiploid (males from unfertilised eggs)
54
Hemiptera (True bugs): Synapomorphies
| Hemimetabola. Basal neoptera (basal winged insects)
* Mouth parts fused to form piercing, sucking beak or rostrum
* Herbivorous
* Major plant pests
* Disease vectors
* Viviparity and parthenogenesis in some groups
54
Hemiptera - Plant juice issues
| Hemimetabola. Basal neoptera (basal winged insects)
* Phloem sap - contains very little nitrogen - positive pressure
* Xylem fluid - negative pressure - leaf transpiration - low nutrient
* Negative pressure - difficult to get out - insects have to actively work against pressure
* Formation of beak - large muscles in head
55
Sternorrhyncha: psyllids, **aphids**, whiteflies, scale insects
| Hemimetabola. Basal neoptera (basal winged insects). HEMIPTERA
* Fine, hairlike stylets
* Parthenogenetic viviparity
* Reduced or lost ovipositor (birth live young)
* Phloem feeding + honey dew secretion
56
Auchenorrhyncha: **Cicadas**, cercopids, membracids, fulgoroids
| Hemimetabola. Basal neoptera (basal winged insects). HEMIPTERA
* Elaborate acoustic organs on legs
* Enlarged clypeus (forehead)
* Cibarial pump
* Xylem feeding
57
Eusociality
Depends on high levels of altruism within groups as individuals increase the fitness of others at a cost to themselves (e.g., by helping care for young).
58
Heteroptera: Shield bugs
| Hemimetabola. Basal neoptera (basal winged insects). HEMIPTERA
* Beak attached to front of head
* Hemelytrous forewings
* Leathery wings
* Flat folded wings, overlap abdomen
* Scent glands on nymphs (anti-predator)
* Some are predators
59
The 4 big insect orders
| Holometabola
* Coleoptera
* Lepidoptera
* Hymenoptera
* Diptera
60
Coleoptera (Beetles)
| Holometabola
* Very diverse
* 40% of all insects
* Broken up into 4 suborders
* 166 families
* 400-420,000 species
* Diversity in morphology, ecology and behaviour
61
Coleoptera: Synapomorphies
* Hardened front wings - **elytra**
* Large hind wings with specialised venation for tucking and for power flight (allows them to have very large hind wings)
* Reduced thorax
* Retracted genitalia
*Beetles are all very similar in overall appearance - few deviations*
62
Coleoptera: Elytra
* Access to hard habitats and spaces - burrow into wood, leaf etc
* Wing protection
* Infection and predation protection
* Homeostasis (desiccation, cold)
*Key morphological adaptation that allowed massive radiation*
63
Coleoptera: Beetle Ecology Variety
* Most are herbivorous (roots, stems, leaves)
* Fungivorous
* Predaceous
* Peculiar diets (e.g. pure cellulose/lignin; dried grain)
* Parasitic – very uncommon
* Repeated evolution of aquatic adaptations (plastrom - air bubble, used as gill)
64
Coleoptera sub-orders
* Adephaga
* Polyphaga
* Archostemata
* Myxophaga
65
Adephaga
| Coleoptera sub-order
* Mostly predacious
* Diving beetles are mostly predatory
* Dominated by carabidae (ground beetles) and aquatic (diving beetles)
E.g. Bombardier beetles → spray out anti-predator chemical weapon
66
Polyphaga
| Coleoptera sub-order
* Herbivorous
* Form bulk of the coleoptera
* E.g. dung beetles, stag beetles
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Insect sensory perception (4 types)
* Chemoreception
* Mechanoreception (tactile)
* Thermal and hygroreception (heat)
* Visual reception
68
Chemoreceptoin (2 kinds)
* Olfactory - gas phase
* Contact - liquid phase (contact based)
*Sensillae - detect the signals (found on antennae, mouthparts, legs*
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Sensillae
| Insect sensory perception
* Punctured with pores that allow gas to flow in.
* In most insects the part of the brain associated with chemical signals is the largest part of the brain
* Variable sensitivity
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Chemoreception olfaction
| Insect sensory perception
Important for **long distance communication** & **detection** **of mates, resources, predator warning**
Semiochemicals (information chemicals)
* **Pheromones** (within-species communication)
* **Allelochemical** (between species communication)
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Pheromones
Within-species communication
72
Allelochemical
Between species communication
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Striped ambrosia beetle and other beetle that inhabit the same tree
| Chemoreception
Detects other beetles pheromones that colonises the same tree to find a tree for themselves.
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Mechanoreception (tactile)
* Perception of any mechanical distortion of the body
* Allows insect to orientate themself
* Touch, vibration, strain, stress
* Huge range of sensitivity **trichoid sensillum**
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Trichoid Sensillum
| Mechanoreception
* Hairs on insect are attatched to peg below surface.
* When hairs touch something the peg is stimulated and caused the **scolopale** to activate attached nerve cells
* Nerve then sends signal
76
Visual systems
| Insect sensory systems
* **Ocelli** - simplified eyes - generally one lens - multiple rhabdomes - allows response to changes in day length
* **Stemmata** - found in larval insects - provide basic orientation - very simple eye
* **Compound eye**
77
Thermo and hydro-reception
* Heat and water detection
* Water balance and temperature
* Very little know about these receptors
78
Lepidoptera synapomorphies
* **Glossa** - long mouth part
* **Wing setae** modified to form **scales** (modified hairs)
* Median ocellus lost
* Vom Rath's organ - sensory organ
* Fore tibial brush
79
Lepidoptera: Glossa / Proboscis
* Proboscis uncoiling is operated by a pump system
* Actively pumps hemolymph into the proboscis to extend it.
* Powerful cibarial head pump (can suck up half it's body weight in a single feeding even)
80
Lepidoptera: Variation in the proboscis
* Some variation in the proboscis
* Some used for other things - some use hook tip to suck out juices of cells
81
Caterpillar legs
* Six true legs
* Prolegs at the back used to hold onto plants (not true legs)
82
Silk moth domestication
* First domesticated insect
* Can’t survive in the wild anymore
* Destructive practice → larvae killed
* First sex pheromone synthesis
83
Largest suborder of lepidoptera ?
Glossata (125 families)
84
Glossata synapomorphies
* Double layer of wing scales
* Frenate wing coupling (frenulum)
* Frenulum - spur more secure than other types of wing couplings
85
Moth and butterflies in conservation
* Highly reliant on nectar because of glossop
* Highly threatened by climate change
* Declines in moth species richness with increased greyspace (urbanisation)
* Declines in bees and hoverflies too - moths showed largest decline
86
Hymenoptera
Bees, wasps & ants
Wasps are most prolific
87
Evolution within the Hymenoptera
Repeated evolution of:
* Parasitism
* Nectar feeding
* Eusociality
88
Hymenoptera Synapomorphies
* Unique **labio-maxillary complex** (sucking tongue/glossa)
* **Apical, tibial spur** (antennal cleaning). *Wasps*.
* **Hamuli** (wing coupling mechanism) locking system allows them to be good flyers
* **Haplodiploid** (haploid males from unfertilised eggs, diploid females (fertilised)
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Hymenoptera feeding habits
* Can feed on a variety of things
* Chewing mandibles are common
* Also sucking tongue
90
Symphyta
| Major Hymenoptera groups
* Basal group
* Herbivorous caterpillar like larvae
* Sawfly and Woodwasps
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Apocrita
| Major Hymenoptera groups
* Evolution of the wasp waist
* Apodous larvae - legless larvae
92
Chalcidoidea - tiny group within Apocrita
| Major hymenoptera groups
* Small to minute size (~1-2mm)
* **Parasitoids and hyperparasitoids** of other insects
* Phytophagous in galls
* Fig wasps (Agaoninae) are herbivores
* Hairs on wings no veins
93
Ichneumonoidea: group within Apocrita
| Major hymenoptera groups
1. Parasitoids of other insects
2. Notable, often extreme ovipositors
3. Important natural enemies of herbivorous insects (biocontrol)
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Ectoparasitoid
Feeds externally on host, host is paralyzed.
95
Endoparasitoid
Feeds internally on host, via oviposition
96
Primary parasitoid
Parasitizes the primary host
97
Hyperparasitoid
Parasitizes a primary parasitoid
98
Vespoidea
| Major groups in the Hymenoptera
Wasps and ants
99
Formicidae (ants)
| within Vespoidea
* Numerous independent origins of eusociality
* Predacious and herbivorous
* Large colonies
* Farm fungus - Parallels between human agriculture
100
Apoidea (bees and apoid wasps)
* Veggie wasps
* Evolved to use pollen and nectar as food
* **Scopa** - for pollen carrying (hairs that allow sticky adhesion)
Corbiculates
* Have a **pollen basket (corbicula)**
* All bees that store honey (edible to humans)
101
The significance of honey bees
* Livestock - highly domesticated
* Perception of honeybees as 'wild'
* Outcompete wild species of bees
* Disease spreaders
102
Largest family of bees
Apidae (e.g. bumble bees)
* Most bee species are solitary
* Few parasitic
* Few eusocial
103
Bee lifecycle (solo)
* Excavates a chamber
* Collects pollen (pollen ball)
* Lays egg on pollen ball
* Larva hatch and feed on pollen ball
* Turns into pupa
* Emerges when an adult
104
Cuckoo bees lifecycle
* Finds an already dug and prepared nest (of another bee)
* Lays egg on the pollen ball
* First instar larval stage can have hook-like mouthparts to kill other larva
105
Primitive eusocial
* Not as much dimorphism
* Only size differs between queen and workers
* Decisions made by one individual
106
Advanced eusociality
* Morphologically distinct worker and queen
* Swarming: group decisions
107
Evolution of Eusociality
* Termites have very ancient eusociality (triassic)
* Ants then wasps evolved it after
* Bees are the most recent to evolve eusociality
108
Diptera
The flies
109
Diptera Synapomorphies
* Loss of hind wings
* hind wings formed into **Halteres**
* Extreme reduction of the prothorax
110
Diptera minor synapomorphies
* Apical segment of labial palpus modified to labellum - specialised mouthparts
* Kinked wings
* Apodous larvae - legless larvae
* Reduced abdominal spiracle in adult males
111
Diptera: Major groups
* **Nematocera**: Basal long-horned flies. (e.g. crane flies)
* **Brachycera**: Short-horned flies (e.g. houseflies)
* **Clyclorapha**: Hoverflies
112
Origins and evolution within Diptera
Many different origins of feeding habits
* 12 blood feeding origins
* 17 endoparasitism
* 10 ectoparasitism
* 18 flightlessness
* 26 plant feeding
Very diverse in both basal and derived lineages
FLIES ARE VERY DIVERSE
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