Insect Anatomy & Physiology Flashcards
What are the main parts of Insects’ external anatomy?
- Segmented (generally 6+3+11 segments)
- Exoskeleton
- Head (antennae, compound eye, mouthparts)
- Thorax (wings, fore leg, middle leg)
- Abdomen (spiracles, hind leg, cercus, external genitalia)
What is the cuticle (exoskeleton) secreted by?
The epidermis
What are the three layers of the epidermis?
Epicuticle (above), exocuticle (outer) and endocuticle (inner)
What are the two pigments/structural mechanisms that produce the diverse colours of insects?
- Pigmentation is produced by the insect’s own metabolism, sequestered from a plant source or produced by microbial endosymbionts
- Iridescence is caused by microstructures in the surface chitin causing interference at selected wavelengths (light interference)
What are the key structures of the insect head and what are their roles?
- Gena, clypeus, labrum
- Frons
- Antenna (scape, pedicel and flagellum)
- Ocelli and compound eye
- Mandible
- Maxilla and maxillary palp
- Labium and labial palp
Used for food gathering and manipulation, sensory perception and neural integration
Insects can be classified based on their mouthparts. What are the two main types of mouthparts found in insects?
Entognathous: internal mouthparts (e.g. Collembula)
Ectognathous: external moutparts (e.g. most bugs)
What are some of the different classifications of insect mouthparts?
- Mandibulate (e.g. ants): used for manipulating and chewing good, as well as a variety of other behaviours such as defence and transport.
- Suctorial (e.g. true bugs and butterflies/moths): obtain food by sucking up liquids
- Mouth hooks (e.g. fly larvae)
Insect mouthparts are highly derived i.e. multitude of functional mechanisms across insect species.
What are antennae used for and what are its main parts?
- Scape > pedicel > flagellum
- Sensory structures: touch, vibration, chemicals
- Paired and segmented, often reduced or absent in some larval stages
What are the three segments of the thorax?
- Prothorax
- Mesothorax
- Metathorax
One pair of legs per segment, wings on the mesothorax and metathorax
What are the three pairs of legs called, and what are their main parts?
- Forelegs, midlegs and hindlegs
- Coxa > trochanter > femur > tibia (articulated spines) > tarsus > pretarsus > claws
What are some of the names given to legs based on their function?
- Cursorial (to run)
- Raptorial (to seize prey e.g. Mantis)
- Saltatorial (to jump e.g. cricket)
- Natatorial (to swim e.g. Water Boatmen)
- Fossorial (to dig)
- Prehensile (to grasp e.g. knits)
When are the wings fully developed in insects?
In adult stage (imago)
- All winged insects share the same ‘ground plan’ of three zones and eight wing veins, useful for systematic biology
What are the two types of flight that have evolved in insects?
- Direct flight - muscles directly attached to wings (primitive flight - order Odonata)
- Indirect flight: Muscles attached to cuticle, asynchronous muscles (modern flight, most other insects).
What are some of the different kinds of wings?
- Orthoptera (straight wings)
- Coleoptera (shield wings)
- Strepsiptera (turning wings)
- Hemiptera (half wings)
- Diptera (two wings)
- Lepidoptera (beautiful wings)
- Hymenoptera (membrane wings)
- Thysanoptera (tassel wings)
How many segments does the abdomen usually have and what organs are housed here?
- Variable number of segments (6+)
- Reproductive, respiratory and digestive organs
What structures are found in the terminal region of insects?
- Ovipositer (females)
- Cerci: sensory organs, defence/predation (rare)
What kind of respiratory system do insects have and how does it function?
- Insects have an open circulatory system with no blood vessels and no specialised oxygen carrier cells.
- The insect body cavity - the heamocoel is filled with heamolymph
- Gaseous exchange between the air and heamolymph achieved via tracheal system
What is the tracheal system and what are its components? What limitations does this type of respiratory system have on insects?
- Made up of spiracles (openings of the tracheal system)
- Gas exchange occurs via air-filled trachea that sub-divide into a blind end (doesn’t connect to anything), thin-walled tracheoles filled with fluid
- Passive respiration systems like this put a constraint on insect size
How does the tracheal system differ in aquatic insects?
Most aquatic insects have a closed tracheal system, with gills instead of spiracles
What are the three main sections of the insect digestive system and what are their components?
- Foregut (pharynx, oesophagus, crop, salivary gland, proventriculus)
- Midgut (ceaca, Malpighian tubes, ventriculus)
- Hindgut (ileum, colon, rectum, anus)
What part of digestion occurs in the foregut?
- Ingestion, grinding, lubrication, storage, transfer to midgut
- Paired labial/salivary glads to produce saliva
- Saliva adjusts the PH of the food
What function does the midgut provide in digestion, and how does it carry out said function(s)?
- Production of digestive enzymes (primarily in caeca), grinding, absorption of nutrients (primarily in ventriculus)
- Two distinct areas: ventriculus and caeca
- The caeca are seperated from the food by a thin sheath called the peritrophic membrane
What part of digestion occurs in the hindgut?
- Absorption of water/ions, excretion
- Malpighian tubules collect waste from the haemolymph and excrete it into the hind gut
- The rectum reabsorbs water
What kind of muscles do insects have and how do they carry out locomotion?
- Only striated muscles (i.e. with sarcomeres, unlike smooth muscles)
- Muscle Fibers: Insects have muscles made up of many cells. These cells share a common outer membrane called the sarcolemma. This membrane covers and protects the muscle fibers.
- Oxygen Intake: The sarcolemma (muscle cell membrane) is folded inward, creating tiny tunnels called tracheoles. These tracheoles allow oxygen to enter the muscle fibers, providing them with the oxygen they need for energy during movement.
