Final answer:
Flies are attracted to the odors emitted from decomposing flesh and will lay their eggs on a corpse quite soon after death. Forensic entomologists can use the presence of fly eggs and larvae to estimate time of death.
Step-by-step explanation:
Flies typically lay their eggs on decaying flesh soon after death. The presence of polyamines such as putrescine and cadaverine, which are products of protein decay, produce a strong odor that attracts flies to the corpse. Flies are highly sensitive to these odors and often lay their eggs within a short timespan post-mortem. A forensic entomologist can use the lifecycle stages of maggots recovered from cadavers to help determine the time of death. The work of Francesco Redi through his experiments also supports the fact that maggots come from the eggs laid by flies and do not spontaneously generate.