Systematic Entomology BZO5T12

Syllabus topics (RTMNU)

• Foundations of Taxonomy and Systematics: History, scope, and significance of systematics
• Principles of taxonomy
• Homology and analogy
• Cladistics and phylogenetic systematics
• Concepts of monophyletic, paraphyletic, and polyphyletic groups
• Sexual dimorphism in insects
• Classification of Insects: Basis of insect classification across historical periods—Pre-Linnaean, Linnaean, and Post-Linnaean taxonomy
• Major classification schemes (Richards and Davies, Kristensen, Triplehorn and Johnson)
• Modern classification of Class Insecta, hierarchical categories (rank, taxon, category)
• Origin and Evolution of Insects: Origin of arthropods and insects
• Major evolutionary transitions in insects
• Overview of insect phylogeny
• Classification of Superclass Hexapoda—Classes Entognatha (Collembola, Protura, Diplura) and Insecta
• Evolutionary significance of major insect lineages
• Modern Approaches in Systematics and Nomenclature: Molecular systematics
• DNA barcoding
• Cytotaxonomy
• Numerical taxonomy (phenetics)
• Principles of the International Code of Zoological Nomenclature (ICZN)
• Homonymy, synonymy, and type concept in zoological nomenclature

1.1 Foundations of Taxonomy and Systematics

Taxonomy is the science of identifying, describing, naming and classifying organisms. Systematics is wider: it studies the diversity of organisms and their evolutionary relationships (phylogeny). Simpson (1961) defined systematics as "the scientific study of the kinds and diversity of organisms and of any and all relationships among them".

History (brief): Aristotle grouped animals into "with blood" and "without blood" and called insects Entoma (cut into segments); Linnaeus (1758) introduced binomial nomenclature; Darwin (1859) gave the idea that classification should reflect descent; Willi Hennig (1950, 1966) founded cladistics; modern systematics uses DNA data.

Scope and significance: Insects are the largest group of animals (about one million described species). Correct identification is needed for pest control (wrong identification = wrong pesticide or wrong bio-agent), quarantine, disease vector control, biodiversity conservation, forensic entomology and evolutionary studies.

Principles of taxonomy: (1) characters used must be stable and heritable; (2) groups should be natural (based on many shared characters); (3) every taxon gets one valid name under the code; (4) classification is hierarchical; (5) type specimens fix the meaning of names.

Cladistics (phylogenetic systematics): Groups organisms only on shared derived characters (synapomorphies), not on shared primitive characters (symplesiomorphies). Results are shown as a branching diagram called a cladogram.

1. Monophyletic group (clade): An ancestor and all its descendants – e.g. Pterygota (winged insects), Holometabola. Only these are accepted in cladistics.
2. Paraphyletic group: An ancestor and some descendants – e.g. "Apterygota" (wingless insects, excluding winged descendants); traditional Blattodea without termites.
3. Polyphyletic group: Members from different ancestors grouped by convergent features – e.g. grouping all "flying animals" together.

Sexual dimorphism in insects: Differences between male and female of the same species in form, size or colour. Examples: male stag beetles have huge mandibles; male mosquitoes have bushy (plumose) antennae, females hairy (pilose); female glow-worms and bagworm moths are wingless; female termites/queens are enormously enlarged; many butterflies differ in wing colour. Taxonomists must know this so that male and female are not described as different species.

1.2 Classification of Insects

1. Pre-Linnaean period: Aristotle's groups; Swammerdam (17th century) grouped insects by type of metamorphosis; John Ray used wings and metamorphosis.
2. Linnaean period: Linnaeus, Systema Naturae (10th edition, 1758), placed insects in 7 orders mainly on wings – Coleoptera, Hemiptera, Lepidoptera, Neuroptera, Hymenoptera, Diptera and Aptera.
3. Post-Linnaean period: Fabricius used mouthparts; Brauer (1885) divided insects into Apterygota and Pterygota; Sharp (1899) divided Pterygota into Exopterygota (wings develop outside, incomplete metamorphosis) and Endopterygota (wings develop inside, complete metamorphosis); later Hennig's cladistics.

Major classification schemes:

Modern classification of Class Insecta (outline): Archaeognatha and Zygentoma (wingless) → Pterygota: Palaeoptera (Ephemeroptera, Odonata – wings cannot fold) and Neoptera (wings fold back): Polyneoptera (Orthoptera, Blattodea incl. termites, Mantodea, Phasmatodea, Dermaptera, Plecoptera etc.), Paraneoptera (Psocodea, Thysanoptera, Hemiptera), Holometabola (Coleoptera, Neuropterida, Hymenoptera, Lepidoptera, Trichoptera, Diptera, Siphonaptera, Mecoptera).

Hierarchical categories: A category is a level (rank) in the hierarchy – kingdom, phylum, class, order, family, genus, species. A taxon is an actual group at a rank (e.g. Lepidoptera is a taxon at the rank "order"). Rank = the position of a taxon in the hierarchy.

1.3 Origin and Evolution of Insects

1. Origin of arthropods: From segmented marine ancestors in the Cambrian (over 500 million years ago); lobopodians are considered close relatives.
2. Origin of insects: Molecular studies show hexapods arose from within crustaceans (the clade Pancrustacea), not from myriapods as once thought. The oldest hexapod fossil is the springtail Rhyniella praecursor from the Devonian Rhynie chert (about 400 million years ago).
3. Major transitions: (a) move to land – waterproof cuticle, tracheae, Malpighian tubules; (b) origin of wings (Carboniferous; giant griffinflies like Meganeura with about 70 cm wingspan); (c) wing folding (Neoptera) – allowed hiding in crevices; (d) complete metamorphosis; (e) social behaviour (termites, ants, bees); (f) coevolution with flowering plants in the Cretaceous (pollinators, herbivores).

Superclass Hexapoda (six legs, body in head, thorax, abdomen):

Evolutionary significance: Wings gave insects dispersal and escape; small size, high reproduction and metamorphosis allowed them to occupy almost every land and freshwater habitat.

1.4 Modern Approaches in Systematics and Nomenclature

1. Molecular systematics: Uses DNA/protein sequences to build phylogenetic trees; solved problems like the position of termites within Blattodea.
2. DNA barcoding: Identification of species by a short standard gene region – for animals a ~650 base-pair part of the mitochondrial COI (cytochrome c oxidase I) gene (Paul Hebert, 2003). Useful for larvae, damaged specimens and cryptic species. Records are stored in BOLD (Barcode of Life Data System).
3. Cytotaxonomy: Uses chromosome number, shape and banding (e.g. polytene chromosomes of Drosophila and Anopheles sibling species).
4. Numerical taxonomy (phenetics): Sokal and Sneath (1963); many characters given equal weight and grouped by overall similarity using computers; result is a phenogram.

ICZN (International Code of Zoological Nomenclature, 4th edition, 1999):

1. Binomial nomenclature: Genus + species, in Latin or Latinised form, italicised; genus capitalised – e.g. Apis mellifera.
2. Starting point: 1 January 1758 (Linnaeus, 10th edition).
3. Principle of priority: The oldest available name is the valid name.
4. Homonymy: The same name given to two different taxa; the later one (junior homonym) must be replaced.
5. Synonymy: Two or more names for the same taxon; the oldest (senior synonym) is valid, the others are junior synonyms.
6. Type concept: Every name is tied to a type – holotype (the single specimen designated), paratypes (other specimens of the original series), syntypes (when no holotype is fixed), lectotype (later chosen from syntypes), neotype (new type when the original is lost); type species for a genus, type genus for a family.
7. Family-group endings: Family -idae, subfamily -inae, tribe -ini; superfamily -oidea.

Likely exam questions

1. (Long, 8 marks) Explain cladistics and the concepts of monophyletic, paraphyletic and polyphyletic groups. Add a note on homology and analogy.
2. (Long, 8 marks) Describe the origin and evolution of insects and the classification of Superclass Hexapoda.
3. (Short, 4 marks) Write a note on DNA barcoding.
4. (Short, 4 marks) Explain homonymy and synonymy with the principle of priority.
5. (Short, 4 marks) Give examples of sexual dimorphism in insects.

Syllabus topics (RTMNU)

• Ametabola: Thysanura, Diplura, Protura, Collembola — Distinguishing characters, general biology, ecological significance
• Paleopteran Orders: Ephemeroptera and Odonata — Distinguishing characters, general biology, ecological importance
• Orthopteroid Orders (Oligoneoptera): Plecoptera, Grylloblattodea, Orthoptera, Phasmatodea, Dermaptera — distinguishing characters, general biology and ecological significance
• Hemipteroid Orders (Paraneoptera): Psocoptera, Phthiraptera, Thysanoptera, Hemiptera — feeding adaptations, pest status, and vector importance

2.1 Ametabola: Thysanura, Diplura, Protura, Collembola

Ametabola are primitive wingless insects and hexapods with no metamorphosis – the young look like small adults and keep moulting even after becoming adults. Thysanura belong to Insecta; Diplura, Protura and Collembola are now placed in Entognatha.

2.2 Paleopteran Orders: Ephemeroptera and Odonata

Palaeoptera ("old wings") cannot fold their wings flat over the abdomen. Both orders are hemimetabolous with aquatic nymphs (naiads).

Ephemeroptera (mayflies) e.g. Ephemera, Cloeon:

1. Soft body; triangular forewings, small or no hindwings, held upright over the body at rest.
2. Two or three long caudal filaments.
3. Adults have vestigial mouthparts and do not feed; live only a few hours to days ("ephemeral").
4. Unique subimago stage – the only insects that moult once more after getting functional wings.
5. Nymphs aquatic with leaf-like abdominal tracheal gills; feed on algae and detritus.
6. Ecological importance: Food for fish and birds; nymphs are sensitive to pollution, so they are bioindicators of clean water; mass emergences ("hatches").

Odonata (dragonflies and damselflies):

1. Large compound eyes, short bristle-like antennae, chewing mouthparts.
2. Two pairs of similar, net-veined wings with a pterostigma; long slender abdomen.
3. Anisoptera (dragonflies) – hold wings spread horizontally, hindwings broader; Zygoptera (damselflies) – wings held together over body, both pairs similar.
4. Males have secondary copulatory organs on abdominal segments 2–3; mating in a "wheel" position.
5. Nymphs (naiads) aquatic; lower lip forms a hinged, extensible labial mask to catch prey; dragonfly nymphs breathe by rectal gills, damselfly nymphs by three caudal gills.
6. Ecological importance: Both adults and nymphs are predators – eat mosquitoes and their larvae (natural biological control); indicators of wetland health.

2.3 Orthopteroid Orders (Oligoneoptera)

2.4 Hemipteroid Orders (Paraneoptera)

These orders show a trend from chewing to piercing–sucking mouthparts, and many are pests and vectors.

1. Psocoptera (booklice and barklice) e.g. Liposcelis: tiny, soft; swollen postclypeus; chewing mouthparts; feed on moulds, starch – pests of stored grain, books and museum specimens.
2. Phthiraptera (lice): wingless, dorsoventrally flattened ectoparasites of birds and mammals; legs with claws for clinging to hair; eggs ("nits") glued to hair. Chewing lice (bird lice) and sucking lice (Anoplura). Human body louse Pediculus humanus humanus transmits epidemic typhus (Rickettsia prowazekii), trench fever (Bartonella quintana) and louse-borne relapsing fever (Borrelia recurrentis); head louse and crab louse (Pthirus pubis) cause irritation. Livestock lice reduce milk and wool yield. Psocoptera and Phthiraptera are now united as Psocodea.
3. Thysanoptera (thrips): minute; narrow wings with long fringe of hairs; asymmetrical "punch and suck" mouthparts (only the left mandible present). Pests: chilli thrips Scirtothrips dorsalis (leaf curl), onion thrips Thrips tabaci; vectors of tospoviruses such as tomato spotted wilt virus. Some are predators or pollinators.
4. Hemiptera (true bugs, aphids, hoppers): mouthparts a jointed beak (rostrum) with two pairs of stylets inside the labium. Heteroptera have forewings half-leathery (hemelytra); others (aphids, hoppers, whiteflies, scales) have uniform wings.
   • Pests: aphids, whitefly Bemisia tabaci, brown planthopper Nilaparvata lugens (hopperburn of rice), mango hoppers, mealybugs, red cotton bug Dysdercus cingulatus – they suck sap, inject toxins and excrete honeydew (sooty mould).
   • Vectors: aphids and whiteflies transmit plant viruses (e.g. cotton leaf curl, yellow vein mosaic of bhendi by whitefly); kissing bugs (Triatoma) transmit Chagas disease (Trypanosoma cruzi) in America; bed bugs (Cimex) are blood-sucking nuisance pests.
   • Useful: lac insect Kerria lacca (lac culture), predatory bugs.

Likely exam questions

1. (Long, 8 marks) Describe the distinguishing characters, biology and ecological significance of Ephemeroptera and Odonata.
2. (Long, 8 marks) Give an account of the hemipteroid orders with reference to their feeding adaptations, pest status and vector importance.
3. (Short, 4 marks) Write the distinguishing characters of Collembola.
4. (Short, 4 marks) Write a note on phase polymorphism in locusts (Orthoptera).
5. (Short, 4 marks) Give the medical importance of Phthiraptera.

Syllabus topics (RTMNU)

• Blattoid and Related Orders: Blattodea, Mantodea, Isoptera, Embioptera, Zoraptera — distinguishing characters, ecological significance, and social behavior in Isoptera
• Neuropteroid Complex: Megaloptera, Raphidioptera, Neuroptera — distinguishing characters, general biology, and ecological significance
• Panorpoid Orders: Mecoptera, Siphonaptera, Trichoptera — adaptations and medical/veterinary importance
• Introduction to Endopterygota: Evolution of complete metamorphosis
• Adaptive significance of holometabola
• Evolutionary advantages of larval and adult specialization

3.1 Blattoid and Related Orders

Social behaviour in Isoptera:

1. Castes:
   • Reproductives – king and queen (primary), formed from winged alates after the nuptial flight; the queen becomes physogastric (huge abdomen) and may lay thousands of eggs a day; supplementary reproductives replace them if they die.
   • Workers – sterile, blind, wingless; build the nest, collect food, feed others, care for young.
   • Soldiers – sterile, with large head and mandibles, or a nozzle (nasute) that sprays sticky chemicals; defend the colony.
2. Caste determination is controlled by pheromones produced by king and queen and by juvenile hormone levels – nymphs are flexible.
3. Trophallaxis: Exchange of food and gut fluid mouth-to-mouth or anus-to-mouth; spreads gut symbionts and pheromones.
4. Digestion of cellulose: Lower termites carry symbiotic flagellate protozoa in the hindgut; higher termites use bacteria, and fungus-growing termites (Odontotermes) cultivate fungus gardens (Termitomyces).
5. Swarming: Alates leave the colony after the first rains, pair up, shed wings and start new colonies.
6. Nests: Underground, in wood, or large mounds with ventilation shafts for temperature control.

3.2 Neuropteroid Complex

The Neuropterida (Megaloptera, Raphidioptera, Neuroptera) are holometabolous insects with net-veined wings and predatory larvae.

1. Megaloptera (alderflies, dobsonflies) e.g. Sialis, Corydalus: large, soft-bodied adults; wings held roof-like; male dobsonflies have very long mandibles. Larvae (hellgrammites) are aquatic predators with lateral abdominal gills; pupate on land. Indicators of clean streams; fish bait.
2. Raphidioptera (snakeflies) e.g. Raphidia: greatly elongated prothorax ("neck") that lifts the head like a snake; female has a long ovipositor. Larvae live under bark and are predators of soft insects; found mostly in temperate forests.
3. Neuroptera (lacewings, antlions) e.g. Chrysoperla, Myrmeleon: delicate, many-veined wings held roof-like; larvae have sucking jaws (mandible and maxilla form a tube) to suck body fluids of prey. Green lacewing larvae ("aphid lions") eat aphids, whiteflies, mealybugs and mite eggs – mass-reared for biological control in India (cotton, vegetables). Antlion larvae ("doodlebugs") dig conical pits in sand to trap ants.

3.3 Panorpoid Orders: Mecoptera, Siphonaptera, Trichoptera

1. Mecoptera (scorpionflies) e.g. Panorpa: head prolonged into a beak (rostrum) with chewing mouthparts at the tip; male genitalia enlarged and upturned like a scorpion's sting; males offer nuptial gifts (dead insects, saliva) to females. Scavengers; considered close to the ancestors of fleas and flies.
2. Siphonaptera (fleas) e.g. Xenopsylla cheopis, Ctenocephalides felis, Pulex irritans:
   • Adaptations: wingless; body laterally compressed to move between hairs; backward-directed spines and combs (ctenidia) prevent removal; hind legs for jumping (energy stored in the elastic protein resilin); piercing–sucking mouthparts; adults blood-feeders; larvae legless, feed on organic debris and adult flea faeces.
   • Medical importance: rat flea X. cheopis is the vector of bubonic plague (Yersinia pestis) – the bacteria block the flea's proventriculus so it regurgitates them while feeding – and of murine typhus (Rickettsia typhi); chigoe flea Tunga penetrans burrows into human skin.
   • Veterinary importance: cat and dog fleas cause itching, allergy dermatitis and anaemia; they are intermediate hosts of the dog tapeworm Dipylidium caninum.
3. Trichoptera (caddisflies) e.g. Hydropsyche, Limnephilus: moth-like adults with hairy wings (Lepidoptera have scales); larvae aquatic, produce silk from labial glands and build portable cases of sand grains, small stones or plant pieces, or fixed nets to filter food. Adaptations: case gives protection and helps respiration; gills on abdomen. Importance: food for fish, bioindicators of water quality; adult hairs may cause allergy. Closely related to Lepidoptera (together "Amphiesmenoptera").

3.4 Introduction to Endopterygota

Endopterygota (Holometabola) are insects with complete metamorphosis: egg → larva → pupa → adult. Wings develop internally from groups of cells called imaginal discs and appear only in the pupa.

Evolution of complete metamorphosis: It arose once, in the Carboniferous–Permian period (about 300 million years ago); Holometabola form a monophyletic group. One popular idea (the pronymph hypothesis) says the larva corresponds to an extended early nymphal (pronymph) stage, and the pupa corresponds to the nymphal stages compressed into one. It is controlled by hormones: ecdysone causes moulting, and juvenile hormone keeps the insect larval; when juvenile hormone falls, the larva pupates.

Adaptive significance and advantages:

1. No competition between young and adults: Caterpillars eat leaves while butterflies drink nectar; mosquito larvae live in water while adults fly.
2. Division of labour: The larva is a specialised feeding and growing machine; the adult is specialised for dispersal and reproduction.
3. Pupa as a resting stage can survive cold, drought or food shortage (diapause).
4. Exploitation of new habitats – larvae inside seeds, wood, fruits, other insects (parasitoids), water.
5. Great evolutionary success: Holometabola make up the large majority of insect species – the four biggest orders (Coleoptera, Diptera, Lepidoptera, Hymenoptera) are all holometabolous.

Likely exam questions

1. (Long, 8 marks) Describe the social organisation and caste system in termites (Isoptera).
2. (Long, 8 marks) Explain the evolution and adaptive significance of complete metamorphosis in Endopterygota.
3. (Short, 4 marks) Write the adaptations and medical importance of Siphonaptera.
4. (Short, 4 marks) Write a note on the neuropteroid complex.
5. (Short, 4 marks) Give the distinguishing characters of Mantodea and Blattodea.

Syllabus topics (RTMNU)

• Coleoptera: Diagnostic characters
• Major families — Coccinellidae, Scarabaeidae, Cerambycidae, Curculionidae
• Agricultural and ecological importance
• Lepidoptera: Morphology and families — Papilionidae, Noctuidae, Pyralidae, Bombycidae
• Economic importance including pests and sericulture relevance
• Diptera: Families — Culicidae, Muscidae, Tephritidae, Tachinidae
• Role as disease vectors and biological control agents
• Hymenoptera: Families — Apidae, Ichneumonidae, Braconidae, Formicidae
• Pollination, parasitism, and ecosystem services

4.1 Coleoptera (Beetles and Weevils)

Diagnostic characters: (1) forewings hardened into elytra that meet in a straight line down the back and protect the membranous hindwings; (2) chewing (mandibulate) mouthparts; (3) large prothorax; (4) complete metamorphosis – larvae are grubs (scarabaeiform, campodeiform, eruciform) or legless; (5) the largest insect order (about 4 lakh described species).

Agricultural and ecological importance: pests of crops, stored grain, timber; predators for biocontrol; decomposers and dung recyclers; pollinators of primitive flowers; food for many animals.

4.2 Lepidoptera (Butterflies and Moths)

Morphology: (1) wings and body covered with overlapping scales (Greek lepis = scale, pteron = wing); (2) adult mouthparts a long coiled proboscis (formed by galeae of maxillae) for sucking nectar; mandibles absent in most; (3) larva a caterpillar with chewing mouthparts, three pairs of thoracic legs and up to five pairs of fleshy prolegs with hooks (crochets); silk from labial glands; (4) pupa often in a cocoon (moths) or a naked chrysalis (butterflies). Butterflies are day-flying with clubbed antennae; moths are mostly nocturnal with feathery or thread-like antennae.

Importance: pests (larvae eat leaves, bore fruits and stems); silk; pollination by adults; food for birds; butterflies as indicators of habitat quality.

4.3 Diptera (True Flies)

Characters: only one pair of functional (fore) wings; hindwings reduced to club-like halteres used for balance; mouthparts sucking, piercing–sucking or sponging; larvae legless (maggots/wrigglers).

1. Culicidae (mosquitoes): slender; long proboscis; scales on wing veins; females blood-feed (piercing–sucking), males feed on nectar; larvae and pupae aquatic. Vectors: Anopheles – malaria (Plasmodium); Aedes aegypti – dengue, chikungunya, Zika, yellow fever; Culex quinquefasciatus – lymphatic filariasis (Wuchereria bancrofti); Culex tritaeniorhynchus – Japanese encephalitis.
2. Muscidae (house flies, stable flies): house fly Musca domestica has sponging mouthparts (labella); breeds in garbage and dung; mechanical vector of typhoid, cholera, dysentery, diarrhoea and eye infections, carrying germs on legs, hairs and vomit drops. Stable fly Stomoxys calcitrans bites cattle and reduces milk yield.
3. Tephritidae (fruit flies): small flies with picture (patterned) wings; females insert eggs into fruits with a sharp ovipositor; maggots rot the fruit. Oriental fruit fly Bactrocera dorsalis (mango, guava), melon fly Zeugodacus cucurbitae (cucurbits). Controlled by pheromone/parapheromone traps (methyl eugenol, cue-lure) and field sanitation.
4. Tachinidae: bristly, house-fly-like flies whose larvae are parasitoids of caterpillars, beetle larvae and bugs – important biological control agents (e.g. Sturmiopsis inferens against sugarcane borers). One harmful tachinid is the uzi fly Exorista bombycis, a parasitoid of silkworms.

4.4 Hymenoptera (Bees, Wasps, Ants)

Characters: two pairs of membranous wings, hindwing joined to forewing by tiny hooks (hamuli); chewing or chewing-lapping mouthparts; in Apocrita a narrow "waist" (petiole); ovipositor modified into a sting in bees, wasps and many ants; haplodiploidy – males from unfertilised eggs (haploid), females from fertilised eggs (diploid); highest social organisation.

1. Apidae (honeybees, bumblebees, stingless bees): hairy body with branched hairs; pollen basket (corbicula) on hind tibia. Indian species: Apis dorsata (rock bee), A. cerana indica (Indian bee), A. florea (little bee) and the introduced A. mellifera. Castes – queen, workers, drones; communication by waggle dance (Karl von Frisch). Products: honey, wax, royal jelly, propolis, bee venom. Most valuable role: pollination of crops (oilseeds, fruits, vegetables) – apiculture raises yields.
2. Ichneumonidae (ichneumon wasps): slender wasps with long antennae and often a very long ovipositor; larvae are parasitoids of caterpillars and beetle larvae, even those deep in wood – natural pest control.
3. Braconidae: small parasitoid wasps; e.g. Cotesia (Apanteles) on caterpillars, Bracon hebetor on stored product moths; mass-reared for biological control. (The egg parasitoid Trichogramma, widely released in India, belongs to Trichogrammatidae.)
4. Formicidae (ants): elbowed antennae; one or two nodes (petiole) in the waist; eusocial colonies with queens, workers (wingless) and winged males. Ecosystem services: soil aeration and nutrient mixing, seed dispersal, predation on pests (weaver ant Oecophylla smaragdina used in mango and citrus orchards), scavenging. Some protect aphids for honeydew or are invasive pests.

Ecosystem services of Hymenoptera: pollination (food security), parasitism (natural control of pests), decomposition and nutrient cycling by ants, and production of honey and wax.

Likely exam questions

1. (Long, 8 marks) Give the diagnostic characters of Coleoptera and describe the families Coccinellidae, Scarabaeidae, Cerambycidae and Curculionidae with their importance.
2. (Long, 8 marks) Describe the families of Diptera with reference to their role as disease vectors and biological control agents.
3. (Short, 4 marks) Write the economic importance of the family Noctuidae.
4. (Short, 4 marks) Write a note on Bombycidae and sericulture.
5. (Short, 4 marks) Explain the ecosystem services of Hymenoptera.