Entomology Lecture Notes PDF

ENTOMOLOGY  ENTOMOLOGY-“entomon”-insects ,”logus”-study INSECTS ✓ Animals belonging to Phylum Arthropoda,or simply arthropods ✓ Most abundant and diverse group of organisms on earth ✓ Are segmented ,bilaterally symmetrical and possess hard chitinous exoskelet...

ENTOMOLOGY  ENTOMOLOGY-“entomon”-insects ,”logus”-study INSECTS ✓ Animals belonging to Phylum Arthropoda,or simply arthropods ✓ Most abundant and diverse group of organisms on earth ✓ Are segmented ,bilaterally symmetrical and possess hard chitinous exoskeleton and paired jointed appendages  INSECTS AS MAN’S BENEFACTORS Predators-play an important role in maintaining the balance in the environment by feeding on and destroying harmful insects Parasitoids –live on or in the host, kill their host, usually require only one host for development Parasites ✓ Honey ✓ Beeswax ✓ Silk ✓ Shellac ✓ dyes  Apiculture-refers to the rearing of honeybees (Apis mellifera) ✓ Originally for honey,wax,royal jelly and other products Sericulture- refers to the rearing of silkworm (Bombyx mori) for the production of silk (mulberry tree-Morus alba)  DISTINGUISHING CHARACTERISTICS OF INSECTS Insects may be distinguished from other arthropods by the following characteristics; 1. Body with three distinct regions ;HEAD,THORAX and ABDOMEN 2. One pair of antennae 3. Three pairs of legs (a few insects are legless and some larvae possess additional leglike appendages (such as prolegs) on the abdominal segments  DISTINGUISHING CHARACTERISTICS OF INSECTS Insects may be distinguished from other arthropods by the following characteristics; 4. Often one or two pairs of wings, borne by the second and /or the third of the three thoracic segments 5. The postoral appendages of the head typically consisting of mandibles,a pair of maxillae, labrum and labium  THE INSECT BODY WALL 1. Epidermal Cell-cellular layer of the body wall ;secretes molting fluid involved in the growth process 2. Cuticle- non-cellular layer of the body wall; covers the entire body surface and also lines the insect’s air tube lining ,salivary glands and parts of the digestive tracts a. Epicuticle-outermost thin layer which contains cuticulin,wax and cement b. Exocuticle-middle part which gives the cuticle its characteristics strength and resilience.It is formed of chitin (a resistant substance isoluble to water,alcohol,alkali and dilute acids) 3. Basement membrane-separates body wall from internal organs i. HEAD Comprises the globular to capsule like anterior body segment of an insect which bears the eyes, antennae and mouthparts CLASSIFICATION BASED ON HEAD POSITION IN RELATION TO THE LONG AXIS OF THE BODY 1. Hypognathous head-condition wherein the mouthparts are at the right angle to the body axis,e.g. grasshoppers, roaches,mantids,larvae of moths and butterflies 2. Opisthognathous head- condition wherein the mouthparts are projecting backward between the legs,e.g. cicada,bugs,leafhoppers 3. Prognathous head- mouthparts is in line to the body axis -commonly seen in carnivorous and/or forms that burrow in wood or soil -e.g. termites, ground beetle 1. MOUTHPARTS Vary in type depending on the kind of food the insects eat The following are the mouthparts of insects Mandibles-tooth-like structure used for chewing,grinding,tearing or pinching –off solid food -heavily sclerotized, paired and unsegmented Maxillae- helps in putting the food into the mouth -paired segmented structures used for mastication and lie directly behind the mandibles Labrum-“upper lip” which is movable and flap-like structures Labium-“lower –lip” found posterior to the maxillae Hypopharynx-a central tongue like which drops from the membranous floor of the head,and bears the opening of the salivary ducts  TYPES OF INSECT MOUTHPARTS a. Mandibulate or Chewing Type-the mandibles cut off and grind solid food,and the maxillae and labium push it into the esophagous b. Cutting-Sponging Type-the mandibles are produced into sharp blades,and the maxillae into long probing style c. Sponging Type-the mandibles and maxillae are non-functional and the remaining parts form a proboscis with a sponge –like apex called labella d. Chewing –lapping Type-the mandibles and labrum are of chewing type and are used for grasping prey,molding wax or nest materials e. Piercing-Sucking Type- the mouthparts of this group are modified to pierce tissues and suck juices from them f. Siphoning Type-the food either nectar of liquid food already are sucked up by means of a long proboscis composed only of a united galea of each maxillae c. Rasping-Sucking Type-has a cone-shaped beak formed from clypeus,labrum,parts of the maxillae and labium 1. ANTENNAE Elongated, segmented structures of varying designs and sizes Are used for sensory purposes and sometimes for defense 3 main parts; a. Scape-basal segment b. Pedicel- second segment c. Flagellum-whiplike part beyond the pedicel  TYPES OF ANTENNAE a. Setaceous-bristle-like, segments taper distally ,e.g. dragonfly and damselfly b. Filiform- threadlike ,segments nearly uniformly cylindrical in size,e.g. grasshopper,crickets,mole crickets c. Moniliform-beadlike, segments similar in size and nearly spherical in shape,e.g.termites d. Serrate- sawlike,the distal half or 2/3 of the antennal segments more or less triangular ,e.g. click beetle e. Pectinate –comblike ,most segments with long slender lateral process - e.g fire-colored beetles f. Clavate-clubbed,segments gradually increase in diameter distally ,e.g. lady bird beetle Capitate-having a head, terminal segments suddenly enlarged,e.g. sap beetle Lamellate- leaflike,terminal segments expanded laterally to form rounded lobes,e.g. June beetle Geniculate- elbowed, the first segment is long and the following segments are small and going off at an angle to the first,e.g. bees,wasps,ants Plumose-feathery, most segments with whorls of long hair,e.g. male mosquito Aristate –the last segment enlarged and bears a conspicuous dorsal bristle called arista,e.g. house fly 1. EYES a. Compound eyes-located on each side of the head of most adult insects ,which consist of many hexagonal elements known as facets or ommatidia b. Simple eyes or ocelli - are located between compound eyes on the front of the head ii.THORAX ✓ The middle region of the insect body which is connected from the head by a flexible membranous neck (cervix) ✓ Contains 3 distinct segments ;prothorax,mesothorax,and metathorax ✓ Each thoracic segment bears a pair of jointed legs ,and in most adult insects the mesothorax and metathorax each have a pair of wings ✓ Each thoracic segment is composed of hardened plates that give it rigidity,such as; a. Notum-upper plate b. Sternum- lower plate c. Pleuron- side/lateral plate A. LEGS Are articulated appendages comprising 5 movable segments; 1. COXA- the proximal segment that is usually short and stout 2. TROCHANTER – connects the coxa with the femur 3. FEMUR – the stoutest and sometime the largest segment of the leg,in some instances, it is armed with strong spines 4. TIBIA- is often long, slender structure with downward –pointing spines that aid in climbing 5. TARSUS-usually made up of several sub segments called tarsomeres,terminate in a pretarsus TYPES OF INSECT LEGS RAPTORIAL LEGS –grasping forelegs of preying mantis CURSORIAL LEGS- running legs of roaches  FOSSORIAL LEGS- digging forelegs of mole cricket SALTATORIAL LEGS-jumping hindlegs of grasshoppers and fleas NATATORIAL LEGS- swimming legs of aquatic insect POLLEN BASKET FOR GATHERING POLLEN-hindlegs of honeybees CLINGING LEGS-e.g. lice CLASPING LEGS-e.g. aquatic beetles WINGS Insect wings show much diversity, varying in shape, texture and coloration. Some specific types of wings are used to identify insect orders, such as; Elytra- forewings of beetles (Coleoptera) -are thick and hard with uniform texture which is used to protect the soft abdomen Hemelytra- forewing of true bugs (Hemiptera) -are a combination of thick and soft,flexible and almost transparent apex or posterior part Fringed type-wings of thrips (Thysanoptera) -are hair-like along the margins of the central using structures Membranous type- wings of caddishflies (Trichoptera) -are soft, flexible, translucent or transparent with prominent wing vein Halteres-hindwings of flies and mosquitoes (Diptera) -are small knob-like structures which are use for balancing instead of flight Tegmina-forewing of grasshoppers,roaches (Orthoptera) -are leathery frontwings which serves to protect the membranous hindwings and abdomen Hamuli Frenulum ABDOMEN This is the third body region and usually the largest part especially among females It is primarily for reproduction, excretion and digestion because the abdomen bears the genitalia,the anus outwardly and the digestive system inside OTHER IMPORTANT PARTS OF THE ABDOMEN ✓ SPIRACLES-these are external openings of the respiratory system found along the side of the thorax and the abdomen ✓ TYMPANUM OR EAR- this is located on the first abdominal segments in the grasshoppers but may be found elsewhere in the body of other insects -the main auditory organ ✓ CERCI- slender, pointed structures found on the eleventh segment of the abdomen  CLASSIFICATION, NOMENCLATURE AND IDENTIFICATION OF INSECT Definition of terms: 1. CLASSIFICATION-ordering of an organism into a hierarchy of categories 2. NOMENCLATURE- naming of organisms (“Nomen”-name; “Calare”-to call) 3. IDENTIFICATION-major application of classification 4. KEYS- comprise a sequence of paired statements and questions that allow the user to eliminate alternative options and eventually associate the unknown specimens with a name 5. TAXONOMY- involves the theoretical basis for classification and the study of classification schemes  THE CLASS INSECTA ✓ The Class Insecta is divided into orders on the basis of the structure of the wings and mouthparts ,the metamorphosis and on various other characteristics SUB-CLASS APTERYGOTA o Primitively wingless insects o Order Protura-proturans o Order Collembola- springtails o Order Diplura- diplurans o Order Thysanura- bristletails,silverfish  SUB-CLASS PTERYGOTA o Winged insects o DIVISION EXOPTERYGOTA- simple body change during growth (incomplete metamorphosis) o DIVISION ENDOPTERYGOTA – complex body change during growth (complete metamorphosis)  INSECT ORDERS 1. EPHEMEROPTERA- mayflies (“Ephemero”-short-lived or for a day; “ptera”- with wings) 2. ODONATA- dragonflies and damselfly (“Odon”-tooth) 3. PLECOPTERA- stoneflies (“Pleco”-folded or plaited) 4. DERMAPTERA- earwigs (“Derma”-skin) 5. ORTHOPTERA-grasshoppers,crickets (“Ortho”-straight) 6. ISOPTERA- termites (“Iso”-equal) 7. EMBIOPTERA- webspiner (“Embio”-lively) 8. ZORAPTERA- zorapterans (“ (“Zor”-pure;”aptera”-wingless) 9. PSOCOPTERA- psocids (“Psoco”-rub small) 10.MALLOPHAGA- chewing lice (“Mallo”-wool;”phaga”-to eat)  INSECT ORDERS 11. ANOPLURA- sucking lice (“anol”-unarmed) 12. THYSANOPTERA- thrips (“Thysano”-fringe) 13. HEMIPTERA-bugs ( “Hemi”-half) 14. HOMOPTERA- aphids,scale insects, hoppers whiteflies (“Homo” -alike,uniform) 15. NEUROPTERA- antlions, lacewings (“Neuro”-nerve) 16. COLEOPTERA- beetles (“Coleo”- sheath) 17. STREPSIPTERA – twisted-winged parasites (“Strepsi”-twisted) 18. MECOPTERA- scorpionflies 19. TRICHOPTERA- caddisflies (“Tricho”-hair) 20. LEPIDOPTERA- moths and butterflies ( “Lepido”-scale) 21. DIPTERA- flies (“Di”-two) 22. SIPHONAPTERA- fleas (“Siphon”-tube; “aptera”-wingless) 23. HYMENOPTERA- ants,bees,wasps (“Hymeno”-membrane)  INSECT METAMORPHOSIS METAMORPHOSIS The change in the form during the development period after the embryonic development ECDYSIS/MOLTING The process by which an insect shed off old skin (cuticle) to provide enough space to grow Most insects molts at least 3 or 4 times during normal development EXUVIAE Old skin (cuticle) left after molting STADIUM Is the total period between any two molts INSTAR Is the actual insect during a stadium  TYPES OF METAMORPHOSIS 1. Ametabolous/No Metamorphosis-there is no change in the appearance of the young compared to the adult ,except in size and development of reproductive structures or genitalia - Stages of this type are egg,young ,adult - E.g. Collembola,Protura,Diplura ,Thysanura 2. Paurometabolous- simple, gradual or direct metamorphosis in which the immature (nymph) resemble the parent (Adult) except size, wings and genitalia development - E.g. Hemiptera,Orthoptera 3. Hemimetabolous- incomplete metamorphosis in which accessory organs like gills are present in immature which is called naiad - Naiads look differently from adult - Naiad and adult are predatory but feed on different foods - Stages are egg, naiad and adult - E.g. Odonata, 4. Holometabolous- complete metamorphosis where all stages differ in appearance - The stages are egg,larva,pupa adult - E.g. Coleoptera, Hymenoptera  STAGES IN METAMORPHOSIS 1. EGGS- all insects produces from eggs ,which consists of the following; a. YOLK-supplies nourishment to the developing egg b. VITELLINE MEMBRANE- a sheath that covers the yolk c. CHORION- or shell which gives protection to the egg d. MICROPYLE-consists of one or more very minute openings thru which the male sperm enters and fertilization takes place e. OPERCULUM- a lid or cap thru which the young escape 2. LARVA- the young proceeding from the egg - Characterized as the growing,feeding and developing stage that usually cover the longest period in the life cycle - The most damaging stage to the crop  TYPES OF LARVAE a. Eruciform- caterpillar like - Body cylindrical, the head well develop but with very short antennae - With thoracic legs and abdominal prolegs - E.g. Lepidoptera b. Scarabeiform-grub-like - Usually curved,the head well develop - With thoracic legs but no abdominal prolegs - Relatively sluggish and inactive - E.g.Coleoptera c. Campodeiform-body elongated ,resembling bristle tails in the genus Campodea - Cerci and antennae usually well developed - Larvae usually active and predaceous - E.g. Neuroptera d. Elateriform- wireworm –like - Body elongated,cylindrical and hard shelled - The legs short and the body bristles reduced - E.g. Coleoptera e. Vermiform-maggot-like - Body elongated and worm like,legless - With or without well develop head - E.g. Diptera 1. NYMPHS-the active developing stage in paurometabolous insects 2. PUPA- the resting (inactive/quiescent) or reorganization stage of holometabolous insects  TYPES OF PUPA a. OBTECT-with the appendages more or less glued to the body - E.g. Lepidoptera - The pupa in many Lepidoptera is covered by a silken cocoon formed by the larva before it molts to the pupal stage b. EXARATE- with the appendages free and not glued to the body - Such pupa looks much like a pale, mummified adult,and is usually not covered by a cocoon - Occurs in most insects except Lepidoptera and some diptera a. COARCTATE-essentially like an exarate pupa,but remaining covered by the hardened exuviae of the next to the last larval instar,which is called a puparium - Occurs in Diptera 1. ADULT/IMAGO-the final instar in the development of an insect in which all of the external characteristics are well defined - The internal systems fully matured or complete -  REPRODUCTION IN INSECTS -Insects reproduce in several ways a. BISEXUAL REPRODUCTION- both males and females are required - eggs will develop if fertilized by sperm - most insects reproduce this way b. PARTHENOGENESIS- only females are required to reproduce the young -the egg will develop without fertilization (e.g. aphids in the tropics) -in temperate areas, aphids undergo bisexual reproduction sometime in the year and parthenogenesis during summer months a. PAEDOGENESIS- is a special type or an exceptional type of reproduction where the larvae of some hymenopterans are capable of reproducing OVIPAROUS-the eggs are laid and left unattended to hatch VIVIPAROUS-produce live young  THE CONCEPT OF PEST PEST Are species whose existence conflicts with people’s profit ,convenience or welfare Such organisms include principally certain insects,nematodes,bacteria,fungi,weeds, birds,rodents or any terrestrial or aquatic plant or animal life Are living organisms causing economic harm to us and our resources (crops, animals,buildings,clothing and other properties)  PEST CLASSIFICATION 1. based on origin a. exotic pest- are those pests that are introduced from outside locality b. endemic pest-are those pests that are local in origin 2. based on abundance or number a. key or major pest-are usually introduced (exotic pest) - are always present in the field every season at a very high population - are always causing economic damage - usually do not have biological control agents because their natural enemies are left in their original place of origin - e.g. diamond back moth, mango hopper, rice black bug, coconut scale insect etc. a. potential or minor pest-are usually endemic species that are always found in the field at a low population - they do not cause economic damage because their populations are being controlled by many natural enemies - e.g. rice skippers b. occasional pest-are usually strong fliers that can migrate from one place to another - they came usually after drought - e.g. armyworms,cutworms,locusts  STORAGE PESTS ;CLASSIFICATION ACCORDING TO NUMBER Major insect pest- are found frequently in abundance or in great number - E.g. rice weevil, flour beetle Minor insect pest- are usually encountered in small number i. based on feeding habit 1. Phytophagous a. Leaf feeders-orthopterans,most larvae of lepidopterans b. Leaf miners- agromyzid flies c. Stem and root borers-pyralid larvae and cerambycid larvae d. Root feeders- root grubs, mole cricket e. Gall makers- gall wasps f. Sap feeders-leafhoppers,planthoppers,bugs,aphids 2. Saprophagous-feeding on dead organic matter a. General scavenger-cockroaches b. Dung feeders-scarabeid beetles INSECT DECOMPOSERS 3. Mycetophagous-Fungus feeder- 4. Zoophagous (carnivorous)- a. Parasites –lives on other animals o Living on warm blooded animal-sucking lice o Living on other insects-hymenopterous wasps of family Ichneumonidae, Braconidae etc. o Blood feeders-mosquitoes