Third-Instar Necrophagous Fly Larval Crop Contents in Human Remains Identification: An Evidence-Calibrated Critical Narrative Review
Jessica Levina *
Department of Parasitology, Faculty of Medicine, Universitas Kristen Indonesia, Jakarta, Indonesia.
*Author to whom correspondence should be addressed.
Abstract
Human identification can become difficult when decomposition, burning or fragmentation restricts recovery of conventional biological samples. Necrophagous fly larvae may retain ingested human material in the foregut crop, offering an indirect and potentially transient source of DNA. This critical narrative review evaluates the evidence specifically relevant to third-instar larvae, distinguishes crop contents from whole-larva and posterior-gut extracts, and examines whether demonstrated DNA recovery translates into defensible identification of human remains. Scholarly publications available through 24 August 2026 were critically selected with emphasis on direct human-remains studies, experimental feeding investigations, forensic genetics and entomological sampling guidance. Early cadaver-based studies established that both mitochondrial and nuclear markers may be recovered from larval feeding material, and subsequent case reports demonstrated possible comparisons with relatives or known references. Nevertheless, successful recovery is inconsistent, laboratory feeding experiments frequently involve non-human tissues, and evidence on postfeeding DNA persistence remains limited. Third instar is an anatomically useful but inadequate surrogate for recent feeding; crop emptying, interspecific variation, preservation, contamination and analytical choice affect interpretation. Recent work indicates that dissected crops and whole larvae can both yield profiles, but the comparative advantage of either matrix has not been established across settings. A positive genetic result therefore supports a source-level proposition only when a reference comparison, appropriate statistical evaluation and independently documented chain of custody are available. It does not independently demonstrate the timing, location or exclusivity of feeding. Priority needs include blinded multi-site validation, measured feeding-to-collection intervals, paired matrix comparisons, low-template and mixture studies, and harmonised reporting of failures. Larval crop material is best regarded as an additional forensic substrate whose value depends on careful entomological characterisation and disciplined DNA interpretation, not as a replacement for direct sampling of human remains.
Keywords: Forensic entomology, blow fly, larval foregut, short tandem repeats, mitochondrial DNA, human remains, postfeeding interval, evidential interpretation