Effects of Metformin Hydrochloride on Development and Survival in the Blow Fly Chrysomya megacephala (Fabricius)

Chrysomya megacephala (Diptera: Calliphoridae) is a key forensic indicator species used to estimate the minimum postmortem interval (minPMI). However, the presence of pharmaceuticals, such as metformin hydrochloride (an antidiabetic agent) may disrupt insect development and compromise PMI accuracy. This study investigated the effects of metformin on the growth, morphology, and survival of C. megacephala larvae. Five groups were examined: a control and four treatment groups exposed to increasing metformin concentrations. Larval length, weight, developmental duration, and survival were measured. Significant dose-dependent effects were observed: high concentrations caused reduced growth, delayed development, and increased mortality. At 2,100 mg/kg, larval length and weight were reduced by 17.16% and 32.44%, respectively. Morphological abnormalities, including darkened regions and spherical subintegumental particles, were noted, with severity increasing with dose. Electron microscopy confirmed these ultrastructural changes. These findings emphasize the need to consider drug-induced developmental alterations in forensic entomology to improve the reliability of minPMI estimations.