## 3 Results
### Proteomics  
The workflow not only allowed metabolomic analysis, but also allowed proteomic analysis in an integrated manner. In sample preparation, metabolites were extracted and the remaining pellet was pretreated. Proteins were digested into peptides through the FASP method. Subsequently, a C18-based additional desalting step was performed for peptides. As a result, 827, 1005, 947, and 738 pig-derived proteins consumed by maggots were identified on day 3, day 5, day 9, and day 11, respectively. Corresponding proteins are listed in Table S3. Top-scoring proteins were mainly cytoskeletal proteins in abundance, such as ACTB (actin, cytoplasmic 1), ACTA1 (actin, 9 alpha skeletal muscle), TUBB1 (tubulin beta chain), and TUBA1A/1B (tubulin alpha-1A/-1B). In addition, ribosomal proteins (40S/60S ribosomal proteins), which exist at the intersection of the microtrabecular that fixes the form of cell, are also identified with high-scoring. Additionally, all the proteomics raw files were analyzed with the merged insect data base, which includes Scathophaga stercoraria, Sarcinophagidae, and Musca domestica. However, it is difficult to find a significant correlation with PMI due to the small number of identified proteins. A list of the corresponding proteins is attached to Table S4.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**No.** & **Pathway Name** & **Number of** & **Number of Compounds** \\  & **Compounds Found** & **in Pathway** \\ \hline
1 & Purine nucleotides degradation II (aerobic) & 16 & 27 \\
2 & L-tryptophan degradation XI (mammalian, via kynure) & 15 & 41 \\
3 & Superpathway of purines degradation in plants & 15 & 34 \\
4 & Purine nucleotides degradation I (plants) & 15 & 23 \\
5 & Superpathway of purine nucleotide salvage & 14 & 54 \\
6 & Superpathway of lipoxygenase & 12 & 33 \\
7 & Superpathway of NAD biosynthesis in eukaryotes & 12 & 37 \\
8 & Superpathway of histidine, purine, and pyrimidine biosynthesis & 11 & 149 \\
9 & NAD biosynthesis II (from tryptophan) & 11 & 27 \\
10 & Superpathway of guanosine nucleotides degradation (plants) & 10 & 11 \\
11 & Adenosylcoalbumin biosynthesis II (aerobic) & 9 & 101 \\
12 & Adenosylcoalbumin biosynthesis I (an anaerobic) & 9 & 99 \\
13 & L-arginine biosynthesis I (via L-ornithine) & 9 & 32 \\
14 & Superpathway of indole-3-acetate conjugate biosynthesis & 9 & 48 \\
15 & Superpathway of arginine and polyamine biosynthesis & 9 & 48 \\
16 & Superpathway of chorismate metabolism & 9 & 152 \\
17 & L-tryptophan degradation III (eukaryotic) & 8 & 38 \\
18 & L-tryptophan degradation IX & 8 & 28 \\
19 & Superpathway of pyrimidine ribonucleosides salvage & 8 & 29 \\
20 & Superpathway of purine nucleotides de novo biosynthesis I & 8 & 74 \\ \hline \hline \end{tabular}
\end{table}
Table 1: List of top 20 pathways from metabolite datasets.  
Figure 4: Metabolic pathways through the KEGG database, including (**a**) purine nucleotides degradation II (aerobic) and (**b**) superpathway of purine nucleotide salvage. Log2 fold-change quantitative values were for day 5 vs. day 3, day 9 vs. day 5, and day 11 vs. day 9, from left to right, respectively. AMP: adenosine monophosphate; ADP: adenosine diphosphate; ATP: adenosine triphosphate; dADP: deoxyadenosine diphosphate; dATP: deoxyadenosine triphosphate; GMP: guanosine monophosphate; GDP: guanosine diphosphate; GDP: guanosine triphosphate; GTP: guanosine triphosphate; IMP: inosine monophosphate; XMP: xanthosine monophosphate.