Question

Discuss in detail life cycle of Lac insect.

Hint:

Remember: Lac insect life cycle includes egg, crawler (mobile stage), settled nymph, and adult stages. Only crawlers are mobile; males are winged but short-lived. The insect completes 2 generations per year depending on the strain (rangeeni or kusmi).

Answer 1

Step 1: Introduction to Lac insect.
Lac insect (Kerria lacca) is a tiny scale insect that produces lac, a natural resin of commercial importance. It is cultivated mainly in India, Thailand, and Myanmar on host trees like palas, ber, and kusum. Lac is used in making jewellery, sealing wax, polishing materials, and in food and cosmetic industries.
Step 2: Host plants of Lac insect.
The major host plants include:

• Kusum (Schleichera oleosa) - Best for rangeeni strain
• Palas (Butea monosperma) - For kusmi strain
• Ber (Ziziphus mauritiana) - For both strains
• Other hosts: Ficus, Acacia, Shisham

Step 3: Life cycle stages of Lac insect.
The life cycle of lac insect consists of the following stages:

• Egg stage:
  • Female lac insect lays eggs inside its own body (viviparous/ovoviviparous)
  • A single female can lay 200-500 eggs
  • Incubation period: Few hours to 2-3 days
  • Eggs hatch inside the female's body and young ones emerge
• Crawler stage (Nymph - Stage I):
  • Newly emerged nymphs are called crawlers
  • They are tiny, reddish, and have six legs and antennae
  • Crawlers emerge through the anal opening of the mother
  • They remain active for 1-3 days and crawl to find suitable settling sites on tender shoots
  • This is the only mobile stage in the life cycle
  • They insert their proboscis into the bark and start sucking sap
  • Duration: 2-4 days
• Settled nymph stage (Stage II):
  • After settling, nymphs lose their legs and antennae
  • They start secreting lac resin from their body
  • The resin forms a protective cell around them
  • They continue feeding on plant sap
  • Sex differentiation begins at this stage
  • Duration: 15-20 days
• Stage III nymph (Pre-adult):
  • Further development with increased lac secretion
  • Male and female nymphs show distinct development paths
  • Female nymphs remain in the cell and continue growing
  • Male nymphs undergo complete metamorphosis
  • Duration: 20-25 days
• Adult stage:
  • Female adult:
    • Females are wingless, legless, and remain inside the cell
    • They have a sac-like body without distinct segmentation
    • Continue feeding and secreting lac throughout life
    • Attract males through pheromones
    • After mating, they lay eggs and die
    • Life span: 3-4 months
  • Male adult:
    • Males undergo complete metamorphosis (pupal stage)
    • They emerge as tiny, winged insects with legs
    • Reddish in color with two long anal filaments
    • Do not feed after emergence (mouthparts absent)
    • Come out of the cell, search for females, mate and die within 1-2 days
    • Life span: 1-2 days only

Step 4: Mating and reproduction.

• Males emerge from their cells and locate females through pheromones
• Mating occurs through the female's cell opening
• After mating, females continue feeding and developing eggs
• Females are ovoviviparous - eggs hatch inside the body and crawlers emerge
• Each female produces 200-500 crawlers

Step 5: Duration of life cycle.
The complete life cycle duration depends on the strain and season:

• Rangeeni strain: Two crops per year
  • Baisakhi crop: June-July emergence (Rainy season)
  • Katki crop: October-November emergence (Winter season)
  • Total life cycle: 4-5 months
• Kusmi strain: Two crops per year
  • Jethwi crop: May-June emergence (Summer season)
  • Aghani crop: December-January emergence (Winter season)
  • Total life cycle: 5-6 months

Step 6: Economic importance and harvesting.

• Lac is harvested just before crawler emergence
• Twigs with lac encrustation are cut (called sticklac)
• Sticklac is processed to remove resin, dye, and other impurities
• Yield depends on host plant, strain, and management practices