Exploring marking methods for the predatory hoverfly Sphaerophoria rueppellii (Diptera: Syrphidae)

Area of Science:

• Ecology
• Entomology
• Pest Management

Background:

• Hoverflies are vital for ecosystems, acting as pollinators and natural predators of pests.
• Sphaerophoria rueppellii is a hoverfly species utilized in biocontrol for managing aphid populations.
• Mark-release-recapture (MRR) methods require persistent, non-harmful markers to track hoverfly behavior.

Purpose of the Study:

• To evaluate the efficacy and impact of three marking agents (rubidium, fluorescein, fluorescent dust) on S. rueppellii.
• To assess the effects of these markers on hoverfly fecundity, mating, and marking persistence.
• To identify optimal marking strategies for enhancing biocontrol programs using hoverflies.

Main Methods:

• Laboratory experiments were conducted to assess the impact of rubidium chloride (RbCl), fluorescein, and fluorescent dust on S. rueppellii.
• Evaluated parameters included female fecundity, mating success, and the duration of marker detectability.
• Marking persistence was monitored throughout the adult lifespan of the hoverflies.

Main Results:

• No significant differences in egg-laying or survival were observed between marked and unmarked hoverflies.
• Rubidium and fluorescein did not impede mating, whereas fluorescent dust significantly reduced mating success.
• Rubidium and fluorescent dust provided long-term marking, while fluorescein faded within 24 hours.

Conclusions:

• Rubidium and fluorescent dust are promising for long-term hoverfly tracking in MRR studies, though dust requires careful application.
• Fluorescein is unsuitable for extended field studies due to its short persistence.
• Rubidium offers harmless, long-lasting marking but requires specialized equipment and investment.