Identifying Plants with Colourful Sepals for Insect Attraction

The question asks to identify the plant among the options where the sepals serve as the primary colourful structures that attract insects.

Analysis of Options

• Bougainvillea: The vibrant colours in Bougainvillea are due to large, leaf-like structures called bracts, not sepals. The actual sepals are small and inconspicuous.
• Mussaenda: This plant is well-known for its modified sepals. Typically, one or more of the sepals enlarge significantly after flowering and become brightly coloured (often white, pink, or red), effectively mimicking petals to attract pollinators like insects.
• Musa (Banana): Banana flowers are typically enclosed by large, colourful bracts. While the flowers have sepals and petals, they are not the main colourful attractants for insects in the manner described. Pollination often involves bats or insects attracted by nectar and scent.
• Euphorbia: Similar to Bougainvillea, the showy, colourful parts in many Euphorbia species are typically bracts surrounding the actual flower clusters (cyathia), not the sepals themselves.

Conclusion

Based on the analysis, Mussaenda is the plant where the sepals are modified into colourful units primarily responsible for attracting insects.