Species Composition and Succession of Necrophagous Insects on Small Buried Baits in China.

The postburial interval (PBI) can be inferred by using necrophagous insects colonizing the buried corpse. In different seasons, the species composition and succession of necrophagous insects on swine carrion (0.5-0.75 kg) buried at the depths of 30 cm and 60 cm in a Populus alba var. pyramidalis (Bunge, 1854) (Salicales: Salicaceae) grove of Shenyang, China from 2017 to 2019 were investigated. A total of 21 species of necrophagous insects belonging to 5 orders, 17 families were collected. Among them, the species of Phoridae and Platystomatidae were dominant at burial depth of 30 cm and 60 cm in summer and autumn. The species composition and time of colonization of necrophagous insects on the buried baits varied with seasons. Platystoma mandschuricum (Enderlein, 1937) (Diptera: Platystomatidae) and Aleochara puberula (Klug, 1833) (Coleoptera: Staphylinidae), the first arriving insects in spring, occurred on the baits for the longest time, from early June to early December. This work could provide reference data for the PBI estimation in Shenyang and similar geographical areas.

Characterization and Phylogenetic Analysis of the Complete Mitochondrial Genomes of Two Tiny Necrophagous Phorid Flies, Metopina sagittata and Puliciphora borinquenensis (Diptera: Phoridae).

The mitochondrial genome is frequently used for species identification and phylogenetic studies. In this study, we first sequenced and annotated the complete mitochondrial genomes of two phorid species that are forensically important in buried or enclosed environments: Metopina sagittata (Liu) and Puliciphora borinquenensis (Wheeler). The complete mitochondrial genome sequences of M. sagittata and P. borinquenensis were 15,640 bp with an A+T content of 75.97% and 15,429 bp with an A+T content of 75.38%, respectively. Their circular genomes both contained 13 protein-coding genes (PCGs), 22 transfer RNA genes, 2 ribosomal RNA genes, and 1 control region located between rrnS and trnI which was 808 bp for M. sagittata and 746 bp for P. borinquenensis. All the PCGs of both species started with ATN codons except for cox1 which used TTG codon. In addition to the common stop codon TAA and TAG, the incomplete stop codon T was used in two PCGs (cox1 and nad4) of M. sagittata and five PCGs (cox1, cox2, cox3, nad5, and nad4) of P. borinquenensis. There were 3 and 10 mismatched base pairs in the tRNA secondary structures from M. sagittata and P. borinquenensis, respectively. Both maximum likelihood and Bayesian inference analyses indicated that Platypezidae and Phoridae are sister taxa. M. sagittata is closely related to P. borinquenensis within the subfamily Metopininae. This work enhances the databases of Phoridae genomes and contributes to the further study of species identification and phylogenetics of this family.

Intrapuparial Age Estimation of Forensically Important Dohrniphora cornuta (Diptera: Phoridae).

Dohrniphora cornuta (Bigot) is a forensically important phorid fly indoors and in burial environments. The determination of a minimum postmortem interval (PMImin) often relies on the determination of the age of the immatures. Although the larval development data of D. cornuta under different temperatures has been established, the intrapuparial stage which lasts for about half of the total immature development is scarce. In this study, we investigated the key morphological changes during intrapuparial development at constant temperatures (15, 18, 21, 24, 27, 30, 33, and 36°C), with an aim to estimate the intrapuparial age of D. cornuta. Puparia were sampled at 12-h (24, 27, 30, and 33°C), 24-h (18 and 21°C), and 48-h (15°C) intervals. The morphological developments within the puparium were analyzed using a stereomicroscope after the puparium was removed. The average minimum duration of intrapuparial stage was inversely related to temperature, ranging from 184.79 ± 3.00 h at 30°C to 1102.86 ± 25.55 h at 15°C for female, and 197.40 ± 4.12 h at 30°C to 1175.33 ± 18.55 h at 15°C for male. It did not develop at 36°C. Some morphological traits that changed during development within the puparium could be used as age markers. According to these changes, the intrapuparial stage of D. cornuta was divided into nine stages which could be used for both sexes. This study provides relatively systematic development data of D. cornuta intrapuparial for the estimation of PMImin in forensic entomology.

Pupal age estimation of forensically important Megaselia scalaris (Loew) (Diptera: Phoridae).

In addition to causing myiasis in humans and animals, Megaselia scalaris (Loew) has been reported as a forensically important fly. The determination of a minimum postmortem interval (PMI) often relies on the determination of the age of the larvae and pupae. The pupal stage represents about 50% of the immature development time and the pupal age may therefore serve as an important tool in entomological minimum PMI estimation. The present study focuses on the key developmental processes during metamorphosis of M. scalaris pupae at different constant temperatures (18, 21, 24, 27, 30, 33 and 36°C). The average minimum duration of development from prepupa to adult emergence was inversely related to temperature, ranging from 170.65 ± 1.39 h at 33°C to 608.80 ± 13.26 h at 18°C. The pupa did not develop at 36°C. Some morphological features that changed during development within the puparium could be used as age markers. According to these changes, the pupal stage of M. scalaris was divided into 10 stages which could be used for both sexes.

Pupal age estimation of forensically important Megaselia spiracularis Schmitz (Diptera: Phoridae).

In addition to causing myiasis in humans, Megaselia spiracularis Schmitz has also been reported as a forensically important fly. The determination of a minimum post-mortem interval (PMI) often relies on the determination of the age of the larvae and pupae. The pupal stage represents about 50% of the immature development time and the pupal age may therefore serve as an important tool in entomological PMI estimation. The present study focusses on the key developmental processes during the metamorphosis of M. spiracularis pupae at different constant temperatures (21, 24, 27, 30, 33 and 36 °C). The average minimum duration of development from prepupa to adult emergence was inversely related to temperature, ranging from 177.10±1.65 h at 33 °C to 379.68±2.20 h at 21 °C. The pupa could not develop at 36 °C. Some morphological features that change within the puparium could be used as age markers. According to this, the pupal stage of M. spiracularis was divided into 11 stages which were fit for both sexes.

Morphology of immature stages of Dohrniphora cornuta (Bigot) (Diptera: Phoridae).

Morphology of all larval instars and puparium of Dohrniphora cornuta (Bigot), a most common phorid fly species indoors in China, is presented using scanning electron microscopy. The first instar larva was composed of 12 segments, each of segments 3-11 with six slender tubercles situated dorsally, dorsolaterally, and laterally in transverse row. These tubercles divided into two segments, of which the basal one was smooth, and the brush-shaped distal one was comprised of a cluster of fine spines. Antennae and maxillary palp complex were visible. Two slits could be seen at the posterior spiracle. Besides the presence of anterior spiracle, the tubercles of second instar became stouter than those of first instar and were covered by numerous long bristles from the base to top. The posterior spiracle contained four slits. Third larval instar was similar to second instar. The bubble membrane comprised of ≈120 globules with a pointed tip on their top presented at the segment 5 of third instar larvae. Puparia showed a retracted cephalic region and a pair of distinct pupal respiratory horns on the dorsum. The respiratory horns were long and bore numerous branches from base to apex. The apex of branch with two longitudinal slits was relatively broad and curled dorsally.

A study on morphology of immature stages of Diplonevra peregrina (Wiedemann) (Diptera: Phoridae).

Morphology of all larval instars and puparium of Diplonevra peregrina, a most common phorid fly species indoors in China, is presented using scanning electron microscopy. The first instar larva was composed of 12 segments, each of segments 3-11 with six spicate tubercles situated dorsally, dorsolaterally, and laterally in transverse row. The dorsal tubercles were much longer than the laterals and dorsolaterals. Antennae and maxillary palp complex were visible. The caudal segment was margined by six long, stout tubercles covered by numerous long bristles at the base through the apex. Two slits could be seen at the posterior spiracle. Besides the presence of anterior spiracle, the tubercles of second instar became more stout than those of first instar and were covered by numerous long bristles from the base to top. The posterior spiracle contained four slits. Third larval instar was similar to second instar. The bubble membrane comprised of clusters of small spines presented at the segment 5 of third instar larvae. Puparia showed a retracted cephalic region and a pair of pupal respiratory horns on the dorsum.