Unit6 - Subjective Questions

Diagnostic Characters of Curculionidae:

• Head: Prolonged into a distinct snout or rostrum.
• Antennae: Geniculate (elbowed) and clubbed, usually arising from the middle of the snout.
• Mouthparts: Mandibles are small and located at the tip of the snout.
• Elytra: Hard and usually cover the entire abdomen.
• Larvae: They are apodous (legless), C-shaped, and usually usually internal feeders (borers).

Economically Important Pest:

• Sitophilus oryzae (Rice weevil) - A major stored grain pest.
• Cylas formicarius (Sweet potato weevil).

Comparison between Pieridae and Papilionidae:

Family Noctuidae (Owlet Moths):

• Status: It is the largest family in the order Lepidoptera.
• Adult Morphology:
  • Mostly nocturnal moths with dull coloration (grey/brown).
  • Robust bodies with strong flying ability.
  • Forewings are narrow; hind wings are broad.
  • They possess a tympanal organ on the metathorax.
• Larvae:
  • Most are phytophagous and smooth.
  • Some act as cutworms (hide in soil during the day, cut seedlings at night).
  • Some are semiloopers (reduction in prolegs).
• Agricultural Importance: Contains major polyphagous pests.
  • Helicoverpa armigera (Gram pod borer/Cotton bollworm).
  • Spodoptera litura (Tobacco caterpillar).

Distinguishing Features of Scarabaeidae (Scarab Beetles):

1. Antennae: Lamellate type (the terminal segments are expanded into plate-like structures that can open like a fan).
2. Body: Generally convex, stout, and oval/elongated.
3. Legs: Forelegs are often modified for digging (fossorial).

Nature of Damage (Larvae - White Grubs):

• The larvae are called White Grubs.
• They are scarabaeiform (C-shaped body).
• They live in the soil and feed on the roots of various crops (groundnut, sugarcane, cereals).
• Root damage leads to yellowing, wilting, and easy uprooting of plants.
• Example: Holotrichia consanguinea.

These two families are the primary sources of commercial silk.

1. Bombycidae (Mulberry Silk Moths):

• Key Species: Bombyx mori.
• Importance: Produces Mulberry silk, which constitutes the bulk of world silk production.
• Characteristics: Completely domesticated; larvae feed exclusively on mulberry leaves; adults cannot fly.

2. Saturnidae (Wild Silk Moths):

• Key Species:
  • Antheraea mylitta (Tasar silk).
  • Samia cynthia ricini (Eri silk).
  • Antheraea assamensis (Muga silk).
• Importance: They produce "Vanya" or wild silks. The silk is generally coarser and stronger than mulberry silk.
• Characteristics: Large moths, often with transparent eye-spots on wings; bipectinate antennae.

Both are major families of parasitic wasps, but they differ in venation and morphology:

Morphological Adaptations of Apidae (Honey Bees):

1. Plumose Hairs: The body is covered with branched (plumose) hairs that trap pollen grains effectively when the bee visits flowers.
2. Corbicula (Pollen Basket): The outer face of the hind tibia is concave and surrounded by curved bristles, forming a basket to carry pollen pellets.
3. Pollen Combs and Brushes: Rows of stiff hairs on the inner side of the hind basitarsus (metatarsus) used to groom pollen from the body and pack it into the corbicula.
4. Mouthparts: Chewing-lapping type with a long proboscis (formed by maxillae and labium) adapted for sucking nectar from deep flowers.

Gall Midges (Cecidomyiidae):

• Order: Diptera.
• Description: Minute, delicate flies with long, moniliform (bead-like) antennae adorned with whorls of hair. The wings have reduced venation (few veins).

Damage to Rice (Asian Rice Gall Midge - Orseolia oryzae):

• Stage: The maggot is the destructive stage.
• Mechanism: The maggot crawls down the leaf sheath to the apical bud and lacerates the tissues.
• Symptom: The irritation causes the leaf sheath to grow into a tubular, onion-leaf-like structure called a "Silver Shoot" or "Onion Leaf".
• Result: The affected tiller does not produce panicles (grain), leading to yield loss.

Justification:
Most members of the family Coccinellidae are predators in both larval and adult stages. They actively feed on soft-bodied pests like aphids, mealybugs, scales, and mites, providing natural biological control.

Family Characteristics:

• Shape: Body is hemispherical (convex above, flat below) and oval/round.
• Appearance: Often brightly colored (red, orange, yellow) with spots.
• Head: Partly concealed by the pronotum.
• Antennae: Short and clubbed.
• Tarsi: Pseudo-trimerous (appear 3-segmented, actually 4).

Exceptions: The subfamily Epilachninae (e.g., Epilachna beetles) are phytophagous and are pests of brinjal and cucurbits.

1. Mouthparts:

• Culicidae: Possess piercing and sucking type mouthparts (in females). The proboscis is long and needle-like, containing stylets to pierce skin and suck blood.
• Muscidae: Possess sponging type mouthparts. The proboscis ends in a fleshy labella to mop up liquid food; they cannot pierce intact skin (except specific biting types like stable flies).

2. Disease Transmission:

• Culicidae: Vectors for Malaria (Anopheles), Dengue/Chikungunya (Aedes), and Filariasis (Culex).
• Muscidae: Vectors for enteric diseases like Cholera, Typhoid, and Dysentery (mechanical transmission via hairy bodies/legs).

Reason for name "Longicorn":
They are called Longicorn or Long-horned beetles because their antennae are usually as long as or longer than their body length.

Diagnostic Features:

1. Antennae: Very long, filiform or serrate, arising on prominent tubercles.
2. Eyes: Compound eyes are often notched or emarginated (kidney-shaped) with the antennae arising in the notch.
3. Body: Elongate and cylindrical.
4. Larvae: Called Round-headed borers. They are fleshy, yellowish-white, and bore into the wood of trees (xylem feeders).
5. Example: Batocera rufomaculata (Mango stem borer).

Characteristics of Tephritidae (Fruit Flies):

• Wings: The wings are usually spotted, banded, or patterned (mottled wings).
• Subcostal Vein: The subcostal vein bends apically at a right angle and fades out.
• Ovipositor: Females have a sharp, retractable, sclerotized ovipositor used to insert eggs into fruit flesh.

Economic Impact:

• They are highly destructive pests of fruits and cucurbits.
• Damage: Maggots feed on the internal pulp, causing rotting and fruit drop.
• Quarantine: They are major quarantine pests, restricting the export of mangoes and other fruits.
• Examples: Bactrocera dorsalis (Oriental fruit fly), Bactrocera cucurbitae (Melon fly).

Family Sphingidae (Hawk Moths / Sphinx Moths):

• Body Shape: Stout, spindle-shaped (streamlined) bodies tapering at both ends.
• Flight: Strong, rapid flyers; some can hover like hummingbirds while feeding on nectar.
• Wings: Forewings are long, narrow, and pointed; hind wings are much smaller.
• Proboscis: Very long, sometimes longer than the body, kept coiled when not in use.
• Larvae: Known as Hornworms because they possess a distinct dorsal horn on the 8th abdominal segment.
• Pupation: usually occurs in the soil in an earthen cell.
• Example: Acherontia styx (Death's head moth - pest of sesame).

Family Trichogrammatidae:

• Description: They are minute, microscopic Hymenopterans. They possess 3-segmented tarsi and broad wings with rows of microscopic hairs (trichia).
• Role: They are exclusive Egg Parasitoids.
• Biological Control:
  • The female lays its eggs inside the eggs of host pests (mostly Lepidopterans).
  • The wasp larva consumes the contents of the pest egg, killing it before the pest larva can hatch and cause damage.
  • Examples: Trichogramma chilonis and Trichogramma japonicum are mass-reared in laboratories on factitious hosts (like Corcyra eggs) and released in fields to control Sugarcane borers, Cotton bollworms, and Rice stem borers.

Family Tenthridinidae (Sawflies):

• Waist: They differ from typical Apocrita (bees/wasps) by having a broad attachment between the thorax and abdomen. They lack the "wasp waist" or petiole.
• Ovipositor: Females possess a saw-like ovipositor used to slit plant stems/leaves to insert eggs (hence the name "Sawflies").
• Larvae: They are eruciform (caterpillar-like) but differ from Lepidopteran caterpillars by having more than 5 pairs of prolegs (usually 6-8 pairs) which lack crochets.
• Feeding: They are phytophagous pests (e.g., Mustard sawfly, Athalia lugens proxima).

1. Agromyzidae (Leaf Miner Flies) - The Pests:

• Nature: Small flies whose larvae (maggots) feed between the upper and lower epidermis of leaves.
• Damage: They create serpentine mines or tunnels on leaves, reducing photosynthetic area.
• Example: Liriomyza trifolii (Serpentine leaf miner) is a polyphagous pest on vegetables and ornamentals.

2. Tachinidae (Tachinid Flies) - The Beneficials:

• Nature: Usually bristly flies resembling houseflies but with a developed post-scutellum.
• Role: They are parasitoids. The larvae are endoparasites of Lepidopteran caterpillars, Coleopteran beetles, and Hemipterans.
• Significance: They play a crucial natural role in suppressing pest populations (e.g., Sturmiopsis inferens on sugarcane shoot borer).

1. Family Pyralidae (Snout Moths):

• Features: Small to medium moths. Labial palps are often projected forward like a snout. Forewings are elongate/triangular.
• Habit: Larvae are often concealed feeders (borers, webbers, folders).
• Examples:
  • Chilo partellus (Maize stem borer).
  • Scirpophaga incertulas (Yellow stem borer of rice).

2. Family Gelechiidae:

• Features: Small moths (Microlepidoptera). The hind wings are trapezoidal with the outer margin curved/emarginated and have long fringes of hair.
• Habit: Larvae are borers, leaf miners, or seed feeders.
• Examples:
  • Pectinophora gossypiella (Pink bollworm of cotton).
  • Sitotroga cerealella (Angoumois grain moth - stored grain pest).

Family Bruchidae:

• Common Name: Pulse Beetles / Seed Weevils.
• Head: Small, hypognathous, often concealed from above.
• Elytra: Short, exposing the tip of the abdomen (pygidium).
• Legs: Hind femur is often thickened and toothed.
• Life Cycle:
  • Eggs are laid on the surface of legume seeds (in field or storage).
  • Larvae bore into the seed and complete development inside.
  • Adults emerge by cutting a circular exit hole.
• Economic Importance: Most destructive pests of stored pulses (Gram, Moong, Peas).
• Example: Callosobruchus chinensis.

Note: Arctiidae is now often classified as subfamily Arctiinae within Erebidae, but traditionally treated as a family.

Characteristics:

• Adults: Medium-sized moths, often brightly colored (aposematic coloration) with spots or bands (hence "Tiger Moths").
• Defensive Mechanism: They possess tymbal organs on the metathorax to produce ultrasonic clicks to confuse bats.
• Larvae:
  • Densely covered with long hairs or setae.
  • Commonly called "Woolly Bears" or "Hairy Caterpillars".
  • The hairs can cause irritation to human skin.
• Damage: Larvae are defoliators.
• Example: Amsacta moorei (Red Hairy Caterpillar) - a polyphagous pest causing devastation in Kharif crops.