Post-Feeding Larval Mobility and Burial Behaviour of two Forensically Relevant Species, Peckia (Peckia) chrysostoma (Wiedemann) and Peckia (Sarcodexia) lambens (Wiedemann) (Diptera: Sarcophagidae)

In forensic entomology (FE), understanding larval dispersal is crucial for determining key data such as the time, distance, trajectory, speed, and burial depth for pupation. This study aimed to characterize the mobility, horizontal dispersal and burial behaviour of larvae of two forensically important species of Sarcophagidae: Peckia (Peckia) chrysostoma (Wiedemann) and Peckia (Sarcodexia) lambens (Wiedemann). To achieve that, we designed and assessed the efficacy of a Larval Mobility Arena (LMA). Third-instar larvae of each species were released in the centre of the LMA and the following variables were quantified: speed, trajectory orientation, distance travelled, time to reach the soil, and time to burial. Peckia (P.) chrysostoma showed a higher speed (x̄ = 1.58) (P = 0.002) and a greater total distance travelled (x̄ = 61.58) (P = 0.04) compared to P. (S.) lambens (speed x̄ = 1.31; total distance travelled x̄ = 53.21). Mobility in Peckia (P.) chrysostoma was oriented, with displacements concentrated towards specific directions in the arena, whereas P. (S.) lambens displayed a scattered dispersal. The larvae moved fast and quickly reached the substrate for pupation, but the time spent in the arena was longer for P. (S.) lambens (x̄ = 84.12) (P < 0.001). Larvae of both species immediately buried themselves once they encountered the substrate, with no differences in burrowing time (P = 0.68). These findings improve our understanding of larval behaviour and its applications in forensic entomology, supporting experts in locating larvae, inferring parameters of dispersal distances, and improving the accuracy of minimum post-mortem interval estimation.