Understanding the developmental dynamics and temperature sensitivity of avian vampire fly (Philornis downsi) eggs: A dual-study approach

Abstract

The Galápagos Islands, known for their unique and diverse ecosystems, face a significant threat from the invasive parasitic fly, Philornis downsi, which endangers 17 endemic passerine bird species. The introduction of P. downsi, likely via produce cargo from Ecuador, has resulted in substantial reductions in nesting success across the archipelago, prompting urgent research for effective control methods. This study aims to enhance the lab-rearing efficiency of P. downsi by investigating the effects of temperature on egg development and creating a developmental reference. Eggs were collected and subjected to various temperatures (20, 25, 32, and 36 °C) to monitor hatching times and developmental stages through manual and automatic imaging techniques. Results indicate that lower temperatures significantly prolong hatch times, with the 20 °C group exhibiting the longest mean hatch time of 195.65 hours. In turn, higher temperatures accelerated development, with the 32 °C group showing the shortest mean hatch time of 43.8 hours. Four main developmental phases were identified, contributing to a preliminary reference for future research. These findings support the hypothesis that higher temperatures correlate with faster egg development and suggest that temperature manipulation could improve captive rearing outcomes. Enhanced understanding of P. downsi egg development will aid in refining control strategies, crucial for protecting the Galápagos’ endemic avifauna. Further research should explore additional temperature ranges and their impact on the fitness and reproductive success of lab-reared P. downsi.