Insect mouth parts, Insect wing and its types and different systems of Insects

Entomology topics for Forestry students and teachers also.

1. Insect mouth parts   Labrum - a cover which may be loosely referred to as the upper lip. Mandibles - hard, powerful cutting jaws. Maxillae - 'pincers' which are less powerful than the mandibles. They are used to steady and manipulate the food. They have a five segmented palp which is sensory and often concerned with taste. Labium - the lower cover, often referred to as the lower lip. It actually represents the fused pair of ancestral second maxillae. They have a three segmented palp which is also sensory. Hypopharynx - a tongue-like structure in the floor of the mouth. The salivary glands discharge saliva through it.

2. In general, insect mouthparts are modified, paired appendages used to capture, manipulate and chew food (with the exception of the labrum, which is unpaired). The  labrum  is a sclerite or plate that acts as the 'upper lip' in insects that have chewing mouthparts. It essentially forms the roof of the mouth and is useful for pulling food into the mouth. It moves longitudinally (i.e. an up and down motion) and is hinged to the  clypeus . The  mandibles  are the first pair of jaws in insects, moving laterally (i.e. from side to side) when in use. Mandible shape is strongly influenced by function and is therefore highly variable. For example a chewing insect will have strong tooth-shaped mandibles while in a sucking insect they will be thin and needle-shaped. Mandibles are used to cut, chew and tear food as well as to carry objects, fight and mould materials such as wax or soil.

3. The  maxillae  form the second pair of jaws and are located behind the mandibles. Maxillae are used for handling food and moves laterally much like the mandibles. Maxillae posses segmented palps and are structurally more complex than the mandibles. The  labium  is a fused structure that forms the 'lower lip' or floor of the mouth in chewing insects. The labium is often regarded as the 'second maxilla' as it evolved from paired maxillae-like structures which are fused along the centre line. The labium moves longitudinally and possesses a pair of segmented palps . It is used to close the mouth from either below or behind, depending on its exact position.

4. Chewing mouth: Mouth parts that are modified for chewing i.e grass hopper Sucking mouth parts: Mouth parts that are modified for sucking. i.e laces etc

5. WIngs Types of Insect Wing 1. Membranous: e.g. Dragons Fly Honeybee and Termites:  Wings are thin and transparent. They are supported by a system of tubular veins. They are useful in flight. 2. Fringed: e.g. Thrips :  Wing lamina is usually reduced in size. Wing margins fringed with long setae. These insects literally swim through the air. 3.   Haltere : e.g. Hand Wings of Housefly:  Wings are modified into small knobbed vibrating organ called halters, which act as balancing organs and provided the needed stability during flight. 4.

6. Scaly: e.g. Moths and Butterflies:  Wings are covered with scales which are unicellular, flattened outgrowths of the body wall. Scales are responsible for colour . They are important in smoothening the airflow over wings and body. They also insulate the insect against cold. 5. Tegmina : e.g. Forewings of Grasshopper and Cockroach:  Wings are leathery or parchment-like. They are protective in function. They are not useful for flight. 6. Elytra: e.g. Forewings of Beetles and Weevils:  Wing is heavily sclerotized and thick. Wing venation is lost. Wing is tough and protective in function. It protects the hindwings and the abdomen. It is not used for flight. In flight they are kept at an angle to allow free movement of the hindwings . 7. Hemelytra: e.g. Red Cotton Bug:  The basal half of the wing is thick and leathery. The distal half is membranous. They are protective in function and not involved in flight.

7. Reproduction Reproduction Grasshoppers reproduce sexually (male/female fertilization.) Only full grown grasshoppers have reproductive organs. Eggs are produced in the ovaries (female) and sperm in the testes (male.) When sperm enters the female body it is stored in the seminal receptacle. Eggs are fertilized in the oviduct, then leave the females body. At the end of the females body is a hard four-pointed organ  called an ovipositor, which is used to dig holes for the eggs. The eggs are laid in the fall, but dont hatch until spring. Eggs go through incomplete metamorphosis

8. Circulatory system Circulatory A grasshopper has an open circulatory system which means the blood flows into open spaces or sinuses. The blood is colorless because it contains no hemoglobin. The blood transports food and waste but not oxygen or carbon dioxide. Along the dorsal surface of the grasshopper is the aorta and a tubular heart as well as a large pericardial sinus and a large sternal sinus. Contractions of the heart pump da blood through the aorta to the head. In most open systems the blood moves slowly but systems are efficient enough to meet the needs of the organisms.

9. Nervous system Nervous Has more complex behavior than earthworms ( has a highly developed nervous system.) Consists of a brain (head region) , a part  of the ventral nerve cords (throughout the  body) and a ganglion (nerves branch out from here throughout body.) Has eyes ( compound and simple), antennae (feelers) and taste organs (respond to chemical stimuli) and are sensitive to sounds (using tympanum.)

10. Excretory system Excretion Excretory organs are malpighian tubules. They have open circulatory systems so the excretory organs are bathed directly by the blood. Waste from celomic fluid enters the tubules by diffusion. Then the waste passes into the intestine. Water and other nutrients are reabsorbed both in the tubules and the intestine. These are returned to body fluids. Dry waste is called uric acid and is passed from the body, along with feces, through the anus.

11. Digestive system Digestive The grasshopper has a tubular digestive system. Food enters the mouth and is mechanically broken down, and then mixed with saliva by salivary glands. Food is then transported from esophagus to the crop (temporary storage place.) Chitinous teeth-like plates, which grind food, are seen in the muscular gizzards. [Gastric mil (gizzard and crop).] Chemical digestion takes place in the stomach. Gastric caeca surround stomach. They contain cellulose digesting bacteria . In intestines products of digestion are absorbed by the body through the blood stream. Then solid waste is excreted via anus

12. Respiratory system Respiration Does not depend on the circulatory system. Blood does not need to carry carbon dioxide and oxygen. Air is carried directly to cells by the tracheal tubes. Air enters and leaves through 10 pairs of openings called spiracles. The tracheal tubes branch out into smaller tubes. These tubes have fluid filled ends that connect to the cells. This is where the actual respiration takes place. Oxygen diffuses from the tubes into the cells, carbon dioxide from the cells enters the tubes. Oxygen is pumped through the tracheal tubes by muscle contraction. Small air sacks contribute to pumping the oxygen through the tubes.

13. Insect wing Insect wings  are adult outgrowths of the  insect exoskeleton that enable  insects  to fly. They are found on the second and third thoracic segments (the mesothorax and metathorax ), and the two pairs are often referred to as the forewings and hind wings , respectively, though a few  insects  lack hind wings , even rudiments.

14. Types of insect wing 1 . Membranous: e.g. Dragons Fly Honeybee and Termites:  Wings are thin and transparent. They are supported by a system of tubular veins. They are useful in flight. 2. Fringed: e.g. Thrips :  Wing lamina is usually reduced in size. Wing margins fringed with long setae. These insects literally swim through the air. 3.   Haltere : e.g. Hand Wings of Housefly:  Wings are modified into small knobbed vibrating organ called halters, which act as balancing organs and provided the needed stability during flight. 4. Scaly: e.g. Moths and Butterflies:  Wings are covered with scales which are unicellular, flattened outgrowths of the body wall. Scales are responsible for colour . They are important in smoothening the airflow over wings and body. They also insulate the insect against cold. 5. Tegmina : e.g. Forewings of Grasshopper and Cockroach:  Wings are leathery or parchment-like. They are protective in function. They are not useful for flight. 6. Elytra: e.g. Forewings of Beetles and Weevils:  Wing is heavily sclerotized and thick. Wing venation is lost. Wing is tough and protective in function. It protects the hindwings and the abdomen. It is not used for flight. In flight they are kept at an angle to allow free movement of the hindwings . 7. Hemelytra: e.g. Red Cotton Bug:  The basal half of the wing is thick and leathery. The distal half is membranous. They are protective in function and not involved in flight.