1 INTRODUCTION
Sarcophaga peregrina (Robineau-Desvoidy, 1830) (Diptera: Sarcophagidae), commonly known as flesh fly, which is closely associated with human life in ecological habits. The species is widely spread from tropical to subtropical areas of the Palaearctic, Oriental, and Oceanian regions (Xue et al. 2011). Moreover, it is also a large-sized flesh fly with significant body surface features, including the brightly red-tipped eyes, gray and black longitudinal stripes on the thorax, and a checkerboard-like pattern on the abdomen (Majumder et al. 2012) (Additional file 1: Figures S1).
The common carrion-feeding flies mainly include Sarcophagidae, Calliphoridae and Muscidae family, which play a crucial role in forensic investigations associated with decomposed corpses (Byrd& Castner 2010). Compared with the other necrophagous flies, flesh flies are characterized by the reproductive pattern of ovoviviparity (or ovolarviparity), depositing eggs which immediately hatch into larvae onto carrion (Goff et al. 1989; Majumder et al. 2014). The reproductive cycle of S. peregrina comprises three definite stages, including larva, pupa and adult. The mode of reproduction appears to be the result of adaptive evolution, making them more competitive compared to other species. Given that this reproduction reduces the stage of larval development (the time when eggs hatch to first larvae), the species can be used very accurately to estimate the postmortem interval (PMI) of decomposed corpses, and it is therefore an important necrophagous flesh fly in the field of forensic entomology (Byrd& Castner 2010). For instance, S. peregrina is one of the most common species of insect succession patterns on cadavers as well as at many death scenes colonizing on a corpse (Guo et al. 2014; Siti Aisyah et al. 2015; Sukontason et al. 2010; Wanget al. 2017a), which would provide valuable data for forensic investigations, especially floating corpse cases and indoor death-scene (Tomberlin et al. 2011). Recent studies on the species have mainly focused on the effect of drugs and heavy metals (eg. cadmium) on growth and development of larvae (Goff et al. 1989; Wu et al. 2013), molecular identification (Wells& Stevens 2008), larval morphology (Sukontason et al. 2010), cuticular hydrocarbon composition in pupal exuviae for taxonomic differentiation (Gongyinet al. 2007), as well as the developmental data collection at constant temperatures (Wang et al. 2017b).
S. peregrina has also profound implications for human hygiene and the livestock economy. It is an important sanitary insect pest and one of the vector fly species of intestinal infectious diseases and parasitic diseases in human and livestock, and as an ectoparasite causing myiasis (parasitic infestation) in human and other mammals (Leeet al. 2011). They can cause myiasis in the hospital environment which is also called nosocomial myiasis (Miura et al. 2005). As such, the species is considered as an indicator of wound care neglect, either by the nurses or oneself (Nazni et al. 2011). Additionally, in off-shore islands, the larvae of this species are also the key pest of meat industries, which take nutrient from uncovered meat and contaminate food material, ultimately leading to economic losses in the livestock industries (Majumder et al. 2012).
Although S. peregrina possesses ecological, medical and forensic importance, there are few genomic resources for the family Sarcophagidae (Agrawal et al. 2010; Martinson et al. 2019), which seriously hinder the investigation of the specific mechanisms of biological phenomena from the perspective of genomics, transcriptomics and epigenetics. Fortunately, with the emergence of next-generation sequencing technology, genomics and transcriptomic have been recently developed for dipteran flies (Anstead et al. 2015; dos Santoset al. 2014; Kim et al. 2018; Scott et al. 2014), which serve as a reference for molecular studies of related species. But due to the defect of short Illumina reads, the combination of SMRT (Single Molecule Real-Time) sequencing and chromosome conformation capture (Hi-C) can anchor the scaffolds into chromosomal levels (Belton et al. 2012; Roberts et al. 2013), which ensure the availability of high-quality reference genome assembly. Here we reported a chromosome-level de novo genome assembly of S. peregrinaand perform comparative analysis with other published dipteran insects in order to enrich our understanding of adaptive evolution in S. peregrina .