Forensic entomology involves the application of insect and other arthropod biology in legal investigations. Imagine a scenario whereby a dead body has been discovered in a wood - one way of estimating how long it has been there is to identify the insects that have colonised it. The first insects to colonise an above-ground body are true flies (order Diptera). They may arrive within minutes of death and deposit maggots (in the case of flesh-flies) or lay their eggs (blowflies) in wounds or in the mouth, eyes or nostrils; houseflies arrive a little later. Blowflies undergo metamorphosis and their life cycle has four stages; egg, larva (maggot), pupa and adult. The larval stage has three distinct substages, instars, and because we know how long each stage lasts, the presence of any stage can be used to date the arrival of the colonising fly. In this podcast, I explore this process of faunal succession, and give details of two real-life murder cases where entomological evidence proved critical.