Impact of Diphenidol and Diquat on the development of Chrysomya megacephala (Fabricius, 1794) (Diptera: Calliphoridae) and their forensic importance

J Med Entomol. 2026 Jul 1;63(4):tjag123. doi: 10.1093/jme/tjag123.

ABSTRACT

Estimation of the minimum postmortem interval (PMImin) based on forensic entomology is susceptible to interference from xenobiotics. This study explored the toxic impacts of Diphenidol and Diquat on the development of Chrysomya megacephala, a vital forensic fly species. Their effects were assessed on insect development, survival, and morphology to establish PMImin correction parameters for poisoning fatalities and improve the credibility of entomological evidence. Larvae were raised at 28 °C with diets containing Diphenidol (40, 80, and 160 mg/kg) and Diquat (25, 50, and 100 mg/kg), corresponding to 0.5×, 1×, and 2× the estimated human LD50. An AB subgroup design was adopted to eliminate sampling bias. The two compounds exhibited fundamentally distinct toxicological profiles with implications for forensic practice. Diphenidol induced a complex, non-linear disruption, causing significant developmental delays (up to 23.33 h) without reducing overall survival. This pattern risks a covert underestimation of PMImin if insect development appears normal but is temporally shifted. In stark contrast, Diquat produced a clear, dose-dependent toxicity, severely retarding growth, reducing pupation and emergence success by up to 40%, and inducing a 6.9% teratogenicity rate at the highest concentration. These overt effects (stunted growth, low population recovery, and morphological anomalies) serve as direct warning signs of potential toxicant presence and associated PMImin estimation errors. This study’s findings differentiate between hidden temporal delays and overt inhibitory toxicity, underscoring the imperative for integrated toxicological and entomological analysis to prevent critical misinterpretations of the forensic timeline.

PMID:42481059 | DOI:10.1093/jme/tjag123