(a) Describe the life cycle of the variegated grasshopper. (b) List five ways through which diseases are spread on crop farms. (c) List six characteristics ...

Answer Details

(a) Life cycle of the variegated grasshopper (Zonocerus variegatus)

The variegated grasshopper undergoes incomplete metamorphosis with three stages:

1. Egg stage: The female lays batches of eggs in egg pods buried in moist soil. The eggs remain in the soil and hatch after the dry season, usually with the onset of rains.
2. Nymph stage: The hatched young ones (nymphs) resemble the adults but are smaller and wingless. They feed on vegetation and pass through several moults (instars), gradually developing wing buds.
3. Adult stage: After the final moult the nymph becomes a fully winged adult with the characteristic variegated (multi-coloured) body. Adults mate, and the females lay eggs, so the cycle continues.

(b) Five ways diseases are spread on crop farms

• By insect vectors (for example aphids and whiteflies transmitting viruses).
• Through infected planting materials such as seeds, cuttings and tubers.
• By wind carrying fungal spores.
• By irrigation and rain water carrying pathogens from plant to plant.
• Through contaminated farm tools, implements and the hands of farm workers.

(Also by soil harbouring pathogens, and by man and animals moving through the field.)

(c) Six characteristics of a good layer

• It has a bright red, well developed comb and wattles.
• It has a soft, large and moist vent.
• It has a wide space (three to four fingers) between the pelvic bones.
• It is alert, active and has bright eyes.
• It has a soft, pliable and expanded abdomen.
• It has bleached (pale) shanks and beak, showing that pigment has gone into egg production, and it lays many large eggs.