Climate change and diapause in the sheep blowfly, Lucilia sericata

Abstract

Lucilia sericata (Diptera: Calliphoridae) is a cosmopolitan blowfly that is responsible for the majority of blowfly strike cases in sheep in Britain and much of Europe. In temperate habitats, they overwinter as diapausing third stage larvae. Diapause is thought to be triggered by declining photoperiods and temperature, which act on both female adults and their larvae. However, the initiation of diapause within the context of climate change is poorly understood. Subsequently, the aim of the work described was to investigate how diapause is triggered in response to different combinations of photoperiod and temperature and to use the data to consider how diapause in Lucilia sericata might change under climate change conditions. Mesocosm experiments exposed L. sericata adults and their larvae to LD 12:12 h or LD 8:16 h photoperiods at 17, 19 or 21˚C. A total of 989 larvae, across 44 experimental repeats, were assessed. Diapause incidence varied strongly with both temperature and photoperiod; the highest proportion entering diapause (54%) was observed at LD 8:16 h and 17˚C, and the lowest (2%) was observed at LD 12:12 h and 19˚C. A 1˚C increase in temperature reduced the odds of diapause by 81% and 56% at photoperiods of LD 12:12 h and LD 8:16 h respectively. This suggests that warmer temperatures are able to markedly reduce the incidence of diapause even under a short day length. Additionally, worst-case predicted increases in autumn temperature are likely to reduce the incidence of diapause in this species of blowfly in the UK. However, at more moderate predictions of temperature increase, there may be some reduction in the incidence of diapause but it is unlikely to alter the clinical incidence of blowfly strike in sheep in the near future.

Date of Award	17 Mar 2026
Original language	English
Awarding Institution	University of Bristol
Supervisor	Lucy Alford (Supervisor) & Richard Wall (Supervisor)