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•The development of Necrobia rufipes was monitored from 22 to 36°C.•The morphological indexes of larvae were measured in vivo.•Developmental models were established which can be used to estimate PMImin.•A linear discriminant analysis and classifiers for N. rufipes instars were determined.•This study provides data for PMImin estimation using N. rufipes. After the death of humans or animals, the odors released at different stages of decay attract various insects, and other arthropods, to the corpses. Therefore, the development of insects, and other arthropods present on corpses, can be assessed to estimate the minimum postmortem interval since death. In general, necrophagous blow flies are the insects that first colonize corpses. With progressing decay, other necrophagous and predatory insects arrive at the corpses, which will develop on or around these either by feeding directly on the corpses or by prey on other immature insects. Beetles (Coleoptera) mainly arrive at the corpses during the later stages of decay, and play important roles in cases with longer postmortem intervals. Necrobia rufipes (De Geer, 1755) (Coleoptera: Cleridae) is an important stored-product species with world-wide distribution. Moreover, it is also a forensically important insect species. At temperatures of 22, 25, 28, 31, 34, and 36°C (±0.5°C), the developmental periods from egg to adult were 113.20±2.96, 66.16±3.22, 50.61±1.95, 38.26±2.48, 37.97±2.40, and 31.20±2.11 days, respectively. In vivo measurements obtained the morphological indexes of larvae. The growth curve and the equation of the relationship between development time, body lengths, and mesonotum widths were simulated. The isomorphen diagram model, the isomegalen diagram model, and the thermal summation model were established. In addition, the widths of head capsules and pronota of larvae at different instars were determined by cluster analysis. Classifiers were created and validated by linear discriminant analysis.

Fall armyworm (FAW) Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) has become a sporadic pest of sugarcane. Since, it is a relatively new pest of sugarcane with the first report of occurrence came in 2018, detailed reports on its biology, ecology and management are lacking in the public domain. The present study reports the biology, ecology and molecular taxonomy of FAW population occurring in sugarcane. FAW in sugarcane passed through six larval instars to attain its pupal stage. The head capsule widths of first through fifth instar larvae of FAW were in the range of 0.260–0.352, 0.400–0.590, 0.652–0.900, 1.010–1.410 and 1.700–2.162 mm with the mean values of 0.284, 0.470, 0.753, 1.154 and 1.908 mm, respectively. FAW could complete its life cycle in 25.5 (male)—27.2 (female) days in sugarcane (cv. Co 86,032) with mean fecundity of 528 eggs under laboratory condition (27 ± 2 °C). The artificial diet developed and used to rear the FAW in laboratory also supported its growth, development and reproduction. FAW could successfully complete its life cycle in 23.1–25.4 days with the mean fecundity of 347 eggs in the artificial diet. We have also constructed age-specific fecundity tables for both cane-reared and diet-reared populations of FAW. Though the generation time and doubling time were on par with each other, the net reproductive rate, which represents the number of female progenies produced per female per generation was 111.5 for cane-reared population as against 62.3 for diet-reared population indicating the supremacy of the natural host in promoting the reproductive traits of FAW. It was also confirmed through the development of mtCOI gene-based DNA barcodes that the FAW population on sugarcane was “R strain”.

Coleoptera, including the family Nitidulidae, are valuable for estimating long-term postmortem intervals in the late stage of body decomposition. This study showed that, under seven constant temperatures of 16, 19, 22, 25, 28, 31, and 34 °C, the developmental durations of Nitidula rufipes (Linnaeus, 1767) from oviposition to eclosion were 71.0 ± 4.4, 52.9 ± 4.1, 40.1 ± 3.4, 30.1 ± 2.1, 24.2 ± 2.0, 21.0 ±2.3, and 20.8 ± 2.4 days, respectively. The morphological indexes of body length, the widths of the head capsules, and the distance between the urogomphi of the larvae were measured in vivo. The regression model between larval body length and developmental durations was simulated for larval aging, and the head capsule width and the distance between the urogomphi at different instars were cluster-analyzed for instar discrimination. Based on the developmental durations, larval body length and thermal summation data were obtained, and the isomorphen diagram, isomegalen diagram, linear thermal summation models, and curvilinear Optim SSI models were established. The lower developmental threshold and thermal summation constant of N. rufipes evaluated by the linear thermal summation models were 9.65 ± 0.62 °C and 471.40 ± 25.46 degree days, respectively. The lower developmental thresholds, intrinsic optimum temperature, and upper lethal developmental threshold obtained by Optim SSI models were 10.12, 24.15, and 36.00 °C, respectively. The study of the immature stages of N. rufipes can provide preliminary basic developmental data for the estimation of minimum postmortem interval (PMImin). However, more extensive studies are needed on the effects of constant and fluctuating temperatures on the development of N. rufipes.

•Dermestes tessellatocollis is a forensically important insect for PMI estimation.•Development of D. tessellatocollis was monitored from 16 to 34 °C.•Development models were constructed which can be used to estimate PMImin.•Developmental threshold temperature and thermal constant were obtained.•Instar determination accuracy was unsatisfactory for application in casework. Dermestidae generally appears on dry corpses and carcasses, especially if mummified or skeletonized. They are forensically important insect species for estimating longer postmortem intervals (PMI). As they develop, Dermestidae larvae undergo multiple larval ecdyses; however, a lack of guidelines for determining the larval instar limits their forensic application. Herein, we explored how temperature impacts the development of Dermestes tessellatocollis Motschulsky, 1860 (Coleoptera: Dermestidae). At seven constant temperatures (16, 19, 22, 25, 28, 31, and 34 °C), the developmental time from egg to adult was 163.87 ± 9.19, 103.56 ± 3.02, 63.59 ± 2.88, 51.49 ± 2.74, 47.86 ± 3.01, 44.62 ± 4.65, and 41.80 ± 4.87 days respectively. Four morphological indexes, including head capsule width, pronotum width, mesonotum width, and body length, were taken in vivo at regular intervals to identify methods for larval instar determination in D. tessellatocollis. The acquired morphological data were used to simulate fitted curves and equations depicting the relationship between the four morphological indexes and instars. From the validation experiment, we could hardly determine a specific instar based on the morphological indexes. The combination of morphometric data (head capsule, pronotum, and mesonotum width) generated the classification accuracy at 100%, 87.5%, 85%, and 93% for the 1st, 2nd/3rd, 4th/5th, and 6th/7th instars, respectively. Nevertheless, the accuracy was unsatisfactory for application in forensic casework. This study provides fundamental development data for adopting D. tessellatocollis in minimum postmortem interval (PMImin) estimations; however, further studies are needed to improve the classification accuracy for the larval instar determination.

Necrobia ruficollis (Fabricius, 1775) (Coleoptera: Cleridae) is an important cosmopolitan storage pest, and also frequently appears on highly decomposed and skeletonized corpses. It is a forensically important species expected to indicate a longer postmortem interval (PMI). Therefore, we investigated the development of N. ruficollis at five constant temperatures between 22 °C and 34 °C. Under temperatures of 22, 25, 28, 31, and 34 °C, the mean (±SD) developmental durations from eggs to adults were 93.00 ± 1.63, 70.67 ± 0.94, 65.33 ± 3.40, 47.33 ± 0.94, and 56.66 ± 8.73 days, respectively. According to the developmental time and accumulated degree hours results, an isomorphen diagram and thermal summation model were generated. The calculated values of developmental threshold temperature and accumulated temperature constant were estimated by a linear model to be 14.51 ± 0.52 °C and 684.12 ± 33.85 degree days, respectively. Lower developmental thresholds, intrinsic optimum temperature, and upper lethal developmental threshold temperature were estimated by a nonlinear model to be 14.61, 25.90, and 34.94 °C. Morphological indexes of larvae were obtained by in vivo measurements. A growth curve and an equation of the relationship between development time and body length were simulated. In addition, the widths of the head capsules and the distance between the urogomphi of larvae at different instars were determined by cluster analysis. Classifiers were created and validated by linear discriminant analysis. These results provide important basic developmental data for using N. ruficollis to estimate the minimum postmortem interval (minimum PMI). However, this study was only conducted under constant temperature, and the applicability of these data to variable temperature conditions needs to be further confirmed.

The Asian cockroach, Blattella asahinai Mizukubo, has expanded its range throughout the southeastern United States since its introduction into Florida. Unlike its closest relative, the German cockroach, Blattella germanica (L.), B. asahinai lives outdoors and can fly. There is little information on the biology and development of B. asahinai, including the number of instars during nymphal development. To estimate the number of instars of B. asahinai, nymphs were photographed, sexed, and the lengths and widths of their pronota were measured digitally. The number of instars of B. asahinai was estimated using Gaussian mixture models with the pronotal data. The most probable model and its clusters were selected to assign individuals to an instar. Instars were also determined by counting the number of cercal annuli of nymphs. Both clustering and cercal annuli indicated that B. asahinai most frequently had six instars when reared at 30°C. Growth did not strictly follow the Brooks-Dyar Rule, because nymphs had different numbers of instars and different growth patterns. Although Gaussian mixture models are not efficient for field sampling experiments, digital measurements may provide a way to estimate instars with live specimens in development studies without handling the animals in a way that may alter growth.

The mature larva and pupa of Graptustriguttatustriguttatus and the mature larva of Peritelussphaeroides are described for the first time. The larvae of Philopedonplagiatum and Tanymecuspalliatus are re-described. Five larval instars were determined in Tanymecus , thereby correcting doubtful data in the literature. The relationship between larval growth, number of larval instars, head width of the mature larva, and the adult weevil is explained using the example of Tanymecus . The nearly constant ratio of subsequent larval instars in head width ratio, termed “growth factor” and derived from Dyar’s ratio, is used for the determination of larval instars. Larval collecting and breeding data are discussed in relation to their significance for the clarification of life-cycles.

Necrophagous beetles are underrepresented in forensic entomology studies despite their undeniable utility for the field. In the present article, information is presented regarding the developmental biology and instar determination of Sciodrepoides watsoni (Spence, 1813), a very common species occurring across the Holarctic region. Wild collected beetles were kept in climate chambers at constant temperature (12, 15, 18, 21 and 28 °C) and their development was regularly documented. Parameters of thermal summation models and standard errors were calculated for each developmental stage. These models may be used for an estimation of post-mortem interval in legal investigations after further validation on local populations of S. watsoni . An additional methodology is introduced for future studies of size-based characteristics, addressing instar identification bias. The methodology provided estimations (mean, standard error and standard deviation) of S. watsoni larval head capsule width for preliminary larval instar determination. The methodology may be used with other morphological features to improve instar determination accuracy.

In this paper, the authors developed a model that computes, for a given species, the most probable instar of a larva based on its individual head capsule width and the size distribution of the last larval instar. The model presented in this paper is specifically for species of curculionid that develop through four immature instars, but can be adapted for species of weevil with a different number of instars or insects of other taxonomic units. The method computes the risk error associated with assigning a larva to any of the possible instars and might not assign a larva if its size falls within the overlapping zone of the size distributions of two successive instars. Thus, this parsimonious method might be widely used, notably for wild-caught larvae, and can be readily used thanks to the R package CINID that we developed for that purpose.

In insects, the frequency distribution of the measurements of sclerotized body parts is generally used to classify larval instars and is characterized by a multimodal overlap between instar stages. Nonparametric methods with fixed bandwidths, such as histograms, have significant limitations when used to fit this type of distribution, making it difficult to identify divisions between instars. Fixed bandwidths have also been chosen somewhat subjectively in the past, which is another problem. In this study, we describe an adaptive kernel smoothing method to differentiate instars based on discontinuities in the growth rates of sclerotized insect body parts. From Brooks’ rule, we derived a new standard for assessing the quality of instar classification and a bandwidth selector that more accurately reflects the distributed character of specific variables. We used this method to classify the larvae of Austrosimulium tillyardianum (Diptera: Simuliidae) based on five different measurements. Based on head capsule width and head capsule length, the larvae were separated into nine instars. Based on head capsule postoccipital width and mandible length, the larvae were separated into 8 instars and 10 instars, respectively. No reasonable solution was found for antennal segment 3 length. Separation of the larvae into nine instars using head capsule width or head capsule length was most robust and agreed with Crosby’s growth rule. By strengthening the distributed character of the separation variable through the use of variable bandwidths, the adaptive kernel smoothing method could identify divisions between instars more effectively and accurately than previous methods.