Insect Biology PDF

## Insect Dominance * Insects belong to phylum of invertebrates called Phylum Arthropoda. * Insect body divided into three parts: head, thorax and abdomen. * Insect head bears one pair of antenna and Compound eyes are present. - Thorax Consists of three segments and three pairs of legs and two pa...

## Insect Dominance * Insects belong to phylum of invertebrates called Phylum Arthropoda. * Insect body divided into three parts: head, thorax and abdomen. * Insect head bears one pair of antenna and Compound eyes are present. - Thorax Consists of three segments and three pairs of legs and two pairs of wings. * The abdomen Consists of eleven segments and no appendages in adult olge ### Reasons of success of insects: 1. Capacity for flight 2. Small size 3. Presence of exoskeleton. Called Cuticle made up of cuticular protein called Chitin.  4. More adaptability 5. Resistance to desiccation 6. Prevention of water loss 7. Higher reproductive potential  8. Dormancy and hibernation ### Harmful effects of Insects: 1. Insect damage Wood @ termites 2. Insect damage stored food @ been weevils, rice weevils and red flourbeetle 3. Insect damage stored product @ silverfish and Carpet beetle. 4. Insect damage plants. - ex eat leaves: Cotton leaf worm. - burrows in stems: Sugar cane borer - feed on fruits: fruitfly - Sat roots: gryllotapla sp * Second type is indirect damage this means that the insect doesn't harm but transmits bacterial or fungal infection. - ex, Viral diseases of potatoes Carried from plant to plant by aphids. - disease:- Potato tuber necrotic ring disease. ### Insects Cause bad effect on health @ housefly, Cockroache and mosquito * There are different species of mosquitoes transmit Certain diseases. 1. malaria Caused by Anopheles 2. dengue fever and yellow fever Caused by Aedes 3. lymphatic filariasis Caused by Culex. 4. Treuch fever and typhus Caused by lice. 5. The Plague Caused by Rat fleas  6. Tsetse flies Cause Sleeping Sickness * Some insects are endoparasites of animals @x torsalofly which Parasitize Cattle. The larvia Cause myiasis in the skin of their hosts. * Ben - Parasitic infection the live animal or human skin by fly larta which grow inside the host while feeding on its tissue. ### Benficial Effects of Insects: 1. pollination ex Bees, flies and wasps 2. Source of food as - Honeyus Durcato its ant bacterial and antioxidant - Royal jelly us improve general healtte and brain function. - Propolis us it is a natural antibiotic 3. production of useful maternal - The silk by silk worm. - Honey cuax is often added to Creames and Cosmatics to make skin soft and has antibiotic Properties 4. Insects are important in food chains @ Aquatic insects from food for the fishes. 5. Scientific tools:, Drosophila used for research in genetics and Physiology 6. Biological Controls. Some insects used to Control pests as mantid and Parasitoid wasps 7. Aesthetic Value: ex Butterflies are Collected for their beauty. ## Insect Morphology * Insect's body is divided into three functional regions (tagmata): 1. Head 2. Thorax 3. Abdomen * Head ws include the mouth parts and the antennae * Thorax us include the legs and the wings * The head of an insect Composed of six fused segments - The anterior part of the head is the frons. - The anterior area below the dorsum of the head, between and behind the eyes is the Vertex. - The area below the Compound eye is the gena. - The liplike Sclerite is the clypeus * Antennae located between or behind. Compound eyes.   - Antenna is useful to detect chemicals. * Antenna Perceives smell, humidity Changes, Variation in temperature, direction * Antenna is useful for hearing in mosquitoes and Communication in ants - structure of insect antenna: 1. Scape us Base of antenna, Permit free movement 2. pedide ws it Contains sence Cell called Johnston's organ 3. Flagellum is may vary in size and form. * Types of Antennae : lamellate - setaceous-clavate-filiform-Plumose - Serrate - moniliform - pectinate - aristate-geniculate * Insects have two types of eyes: - (i) Simple eyes (dorsal and lateral) (ii) Compound eyes * Compound eyes Consists of thousands of ommatidia which are tiny independent units Consists of a cornea, lens and photoreceptor cells. * Mouth parts us Two bases types we recognised: - (1) Biting and chewing type (2) Stucking mouthpart  * Typical mouth part of insect Consists: upper Lip or labrumus forms upperlip protects the mandible and help in closing mouth Cavity.. - Mandibles us paired strongest structure called jaws. They have teeth like molars and incisors That help in Cutting food. * Maxillaeus Sensory organs its Structure is Cardo basal triangular, stripes middle rectangular, Maxillary Palpi lateral paplifer bearing, Lacinia inner lobie, galea outer lobe. * (pro-first) * (meso=middle) * (meta = last) * Labium closes the mouth Cavity from below and divided into Prementum, mentum and Sulomentum the median pair is glossae and outer Paraglossae its function is mainly as gustatory sense organs.. * Hypopharynx it is like tongue located in front/above the labrum * Stucking mouth part. is more advanced, elongated and beak like - (1) Rasping and sucking (ex) thrips (2) piercing and stucking (es) mosquito, fleas, lice (3) Sponging and lapping (ex) housefly (4) Sucking (ex) Butterfly (5) Chewing and stucking (ex) bees. * Thorax divided into three parts. prothorax .mesothorax. metathorax * Each of three thoracic segments Contain one pair of legs. * wings are found only on the mesothorax and metathorax. * Legs The (3) thoracic, pre-, meso and metathorax have pair of legs Each leg. Consists of five segments & Viz, Coxa, trochanter, femur, tibia and tarsus * legs modified for many purposes as & runing Jumping, digging, grasping, Catching, Walking } . male leg modified for grasping females during mating.  * Wings with insects have two pairs of wings Composed of twomembranes of the Cuticle pressed together and supported by viens * In some insects wings are disappeared Completely and becarne wingless insects as silverfish and lice * Abdomen is located behind the thorax • In most insects, the junction between thorax and abdomen is broad, but in Some junction is very narrow appear as "Wasp waist: * Abdomen Consist of eleven segments (as) Silver fish and may flies but more advanced groups sometimes has six or seven (as) Beetles and flees * in many adult insects, there is spiracle (opening to the respiratory System) near to the pleural membrane on each side of ist eight abdominal segments. * Abdominal divided into three parts pregental segments is from one to serven abdominal segments of adult Gental segments us 8th, 9th segments in femal but 9th in male .post-gental segments us segment 10 anel the small segment 11 * Abdominal appendages Cerci Pair of sensory organs located in Segment 11 these are tactile (touch) receptors @ovipositorus infemals in 8th and gth segment fit Goath together to form an egg-laying mechanism. ## Metamorphosis Metamorphosis > four stages with Varying Structure and habit these are * Egg * Larva * Pupa * Adult 1. Egg stage ensures embryonic development. 2. nymph or larva - us nymph is young insed different from adult in wings and genitals. - larva differs from the adult in the morphology and habitat 3. Pupal stage is the resting stage for reorganization. 4. Adult stage is basically for reproduction. Insects has been classify into three groups due to metamorphosis * Ametabola - Paurometabola/hemimelabola - Holometabola 1. Ametabolas Egg - Immature stage - adult (ex) silver fish 2. Paurometabola us Egg - nymph - adult (ex) Cockroach, grasshoppers - Smaller than the adult, have compound eyes and evident wingbuds. - (ex) biting and stucking lice, termites and buys. 3. Hemimetabolaus Egg - Naiad Adult The immature stage in order Odonata and Ephemeroptera is aquatic and Carlled naiad which differ from adult. 4. Holometabola Egg -> Larva -> pupa -> Adult