Larval interactions between two aphidophagous coccinellids in sweet pepper

Area of Science:

• Ecology
• Predator-prey dynamics
• Biological pest control

Background:

• Antagonistic interactions among predators can regulate top-down effects on shared pests.
• Cannibalism and intraguild predation (IGP) are significant interactions among predatory insects.
• Previous studies documented strong cannibalism and asymmetric IGP between Eriopis connexa and Cycloneda sanguinea.

Purpose of the Study:

• To investigate how larval instar influences the intensity and direction of antagonistic interactions (cannibalism and IGP) between E. connexa and C. sanguinea.
• To assess the impact of extraguild prey availability on these interactions and larval behavior.
• To understand the role of larval defensive capabilities and dispersal in mediating intra- and interspecific predation.

Main Methods:

• Laboratory experiments quantifying aggressiveness, attack, and predation rates between larval instars of E. connexa and C. sanguinea.
• Field observations of larval mortality and within-plant distribution under varying extraguild prey conditions.
• Behavioral assays examining larval dispersal patterns in response to prey availability.

Main Results:

• Larval vulnerability to predation varied with instar, with smaller larvae (second instar) being more susceptible to larger predators (fourth instar).
• E. connexa fourth-instars frequently preyed on C. sanguinea second-instars.
• Antagonistic interactions were significantly reduced when extraguild prey were present, and larval mortality was solely influenced by extraguild prey availability.
• Larvae dispersed from plants when prey became scarce and initially aggregated in upper strata when extraguild prey were available before dispersing.

Conclusions:

• Larval dispersal and defensive behaviors are crucial mechanisms that prevent or reduce cannibalism and intraguild predation in these predatory species.
• The presence of alternative prey (extraguild prey) can significantly relax intra- and interspecific antagonistic interactions.
• Understanding these complex interactions is vital for optimizing biological control strategies utilizing these predatory insects.