Nematology- ICAR JRF/SRF 2024

• Phytophagous Ladybird Beetles (Subfamily Epilachninae):
• Feeding Habit: While the vast majority of ladybird beetles (family Coccinellidae) are beneficial predators feeding on aphids, scales, and mealybugs, the subfamily Epilachninae contains strictly phytophagous (herbivorous) species.
• The Hadda Beetle: Epilachna vigintioctopunctata (28-spotted potato beetle) feeds voraciously on solanaceous and cucurbitaceous leaves (brinjal, potato, tomato), skeletonizing foliage by scraping chlorophyll.
• Predatory Coccinellids Listed: Adonia variegata, Illeis cincta (mycophagous on powdery mildew), and Propylea dissecta are beneficial.
• Conclusion: Epilachna vigintioctopunctata is the phytophagous ladybird beetle (Option 2).

Correct option: (2) Epilechna vigintioctopunctata

• Diagnostic Morphology of Brassica Aphids:
• Cabbage aphid (Brevicoryne brassicae): Nymphs and apterous adults are grayish-green covered with a dense mealy, whitish-gray waxy powder (not yellowish-green with filaments).
• Green peach aphid (Myzus persicae): Adults are oval to pear-shaped, yellowish-green to pinkish, with distinct convergent frontal tubercles, not a pointed abdomen.
• Conclusion: Because both morphological descriptions mischaracterize the diagnostic species traits, both Statement (I) and Statement (II) are incorrect (Option 2).

Correct option: (2) Both Statement (I) and Statement (Il) are incorrect

• Major Sucking Pests of Cotton:
• Target Pests of Cotton:
• Aphis gossypii: The cotton aphid (melon aphid), a major pest causing crinkling and leaf curling and secreting honeydew.
• Phenacoccus solenopsis: The invasive cotton mealybug, causing devastating economic losses to Bt cotton across India.
• Other Aphids Listed:
• (A) Lipaphis erysimi: Mustard aphid, infests cruciferous crops.
• (D) Aphis craccivora: Cowpea aphid, infests pulses and legumes.
• Conclusion: Insects infesting cotton are (B) and (C) only (Option 2).

Correct option: (2) (B) and (C) only.

• Ecological Concept of Trophic Levels:
• Statement (I) is correct: A trophic level represents the hierarchical feeding level or nutritional step that an organism occupies in a food chain or food web (e.g., primary producers, primary consumers, secondary consumers).
• Statement (II) is incorrect: The word 'trophic' is derived from the Greek word trophe (meaning 'food' or 'nourishment'), not from Spanish.
• Conclusion: Statement (I) is correct but Statement (II) is incorrect (Option 3).

• Arthropod Molting and Mouthpart Anatomy:
• Statement (I) is incorrect: Apolysis is the initial detachment of the epidermal cells from the old cuticle; ecdysis is the subsequent physical shedding and casting off of the old exuviae. They are distinct sequential stages of the molt cycle.
• Statement (II) is incorrect: Chelicerae are the pincer-like or fanged feeding appendages characteristic of chelicerate arthropods (spiders, scorpions, ticks, mites). Termite soldiers belong to the order Blattodea (mandibulate insects) and possess heavily sclerotized, adapted biting mandibles, not chelicerae.
• Conclusion: Both Statement (I) and Statement (II) are incorrect (Option 2).

Correct option: (2) Both Statement (I) and Statement (Il) are incorrect