Peckia (Euboettcheria) collusor (Diptera: Sarcophagidae) is a necrophagous insect and represents an important role in forensic entomology, as it is always collected at animal/human corpses. Immature sarcophagids are extremely similar in morphological aspects and can be found colonizing both fresh and mummified bodies. Flesh fly larvae are reported to cause accidental myiasis. In the Neotropical regions little is known about the ultrastructure of immature stages of Sarcophagidae. Scanning electron microscopy gives detailed information on the morphological characters, which can help identify the immature forms of the flies. The aim of this study is to identify larvae and puparia of P. (E.) collusor using this methodology. The integument with net-like patches and the shape and disposition of intersegmental spines of the larval instars can be used to distinguish this flesh fly larva. The number of spiracular ramifications is variable at larval instars. The puparia are very similar to third instar larvae, except for the cephalic structures that are retracted. In conclusion, scanning electron microscopy could help entomologists to identify the immature forms of P. (E.) collusor in forensic investigations and consequently serves as a tool in crime scene investigations.