Oviposition site selection in Cactoblastis cactorum (Lepidoptera): constraints and compromises

Area of Science:

• Ecology
• Entomology
• Behavioral Ecology

Background:

• Oviposition behavior in insects is crucial for offspring survival and population dynamics.
• Understanding host plant selection by Cactoblastis cactorum (Opuntia moth) is vital for biological control programs targeting invasive Opuntia species.

Purpose of the Study:

• To investigate the factors influencing oviposition site selection by Cactoblastis cactorum on two Opuntia species (Opuntia ficus-indica and Opuntia aurantiaca).
• To determine the key plant and environmental variables affecting egg stick clumping and site preference.

Main Methods:

• Field assessment of Cactoblastis cactorum egg stick placement on Opuntia plants.
• Analysis of factors including plant size, moth emergence, cladode condition, plant conspicuousness, height above ground, and shelter from wind.

Main Results:

• Oviposition on Opuntia ficus-indica was significantly affected by plant size, moth proximity, cladode condition, and plant conspicuousness, leading to egg stick clumping.
• No species preference was observed despite higher egg predation and lower fecundity on Opuntia aurantiaca.
• Succulent cladodes, specific heights, and wind shelter were favored oviposition sites.

Conclusions:

• Cactoblastis cactorum oviposition site selection is a compromise between maximizing juvenile survival and completing egg-laying.
• Environmental factors like wind and physiological constraints such as wing-loading limit available oviposition sites.