Accumulated Degree Hours Research Articles

Development time, body mass and length of immatures of Paralucilia fulvinota (Bigot, 1877) (Diptera: Calliphoridae) reared under natural conditions in a Central Amazon forest

Blow flies (Calliphoridae) are used in forensic entomology studies, because their life cycle help to determine the minimum post-mortem interval (PMImin). Paralucilia fulvinota (Bigot, 1877) is a forensic indicator and is reported from human corpses in the Amazonian region. Our objectives were to describe the development time of P. fulvinota under natural conditions at Ducke Reserve (Amazonas), provide the accumulated degree-days (ADD) and accumulated degree-hour (ADH), body length and mass of larvae, and the sex ratio of adults. Pregnant females were sampled on a swine carcass. From hatched eggs, we reared stock colonies and observed the immature development under uncontrolled conditions of temperature (24.5 ± 1.3 ºC), rainfall (188 ± 11.5 mm³) and humidity (84 ± 3.9%). Development time was 11 days. Adult sex ratio was 0.86. Larvae gained mass at constant rates through the instars but grew less in length from the second to the third instar. Accordingly, P. fulvinota grows more in mass than in length when in larval stage. The period from first stadium to adults lasted 159.5 degree-days and 3828 degree-hours. Our results may be helpful in providing a more accurate estimate of PMImin on corpses encountered in forested areas of the Amazon region.

The Growth Model of Forensically Important Lucilia sericata (Meigen) (Diptera: Calliphoridae) in South Korea.

Simple SummaryThis study provides a detailed growth data for Lucilia sericata (Meigen) collected in South Korea. With the growth data, authors compared different minimum ADH models and found little differences. However, the logalithmic model was the best fit among differenct models.Development of forensically important Lucilia sericata (Meigen) was analyzed in South Korea. Rearing was replicated five times at seven constant temperatures between 20–35 °C to elucidate changes in accumulated degree hours, based on developmental stage and body length, and 2673 individuals were statistically analyzed. The results indicated that the optimum temperature, the base temperature, and the overall thermal constant were 22.31 °C (±1.21 °C, 95% CI), 9.07 °C, and 232.81 ± 23 (mean ± SD) accumulated degree days, respectively. In the minimum ADH models of each development stage, nonlinear regression graphs were parallel at the immature stages. Based on the scatter plot (n = 973) of immature stages using ADH values and body length, the logarithmic model using Log10ADH as the dependent variable was identified as the best fitting regression model. Additionally, the adjusted R2 value and mean square of error were 0.911 and 0.007, respectively. This is the first forensically focused study on the development of L. sericata for the estimation of minimum postmortem interval in South Korea. In future studies, we intend to study the development of other necrophagous fly species and to identify parameters for the determination of age at post-feeding and pupal stages.

Effect of constant and fluctuating temperature on the intrapuparial development of Sarcophaga argyrostoma (Robineau-Desvoidy, 1830; Diptera: Sarcophagidae).

This study aimes to investigate the effect of constant and fluctuating temperatures on starting times of developmental periods of insect species. For this purpose, Sarcophaga (Liopygia) argyrostoma (Robineau-Desvoidy, 1830), a forensically important species has been chosen. Whether the constant (25°C) and fluctuating (25.2°C averaged over natural conditions) temperatures would make a difference on the timing of intrapuparial development of this species was investigated. First larval instars were placed in rearing cages until they reached post-feeding third larval instar, which is considered the beginning of intrapuparial development. Relevant morphological changes were observed by hourly dissections. At fluctuating temperature treatment, the post-feeding third instar larvae were transferred to containers under natural, open-air conditions. Minimum and maximum starting times of 23 intrapuparial development periods were determined for both treatments. These times, medians, and standard deviations were compared by Mann-Whitney U tests. Accumulated degree hour values were also calculated for these periods. Regardless of temperature treatment, intrapuparial development periods were similar and adult emergence was observed at 289.5 ( ± 1.52) h under 25°C constant temperature and 319 ( ± 1.41) h under fluctuating temperature conditions. No statistical difference was found between the intrapuparial development of S. argyrostoma reared under constant and fluctuating temperatures, except "pupal-adult apolysis" and "checkered pattern on the abdomen becoming distinct" periods. The use of the results obtained when determining the effect of constant and fluctuating temperatures on the starting times of developmental periods of this species in forensic entomology, is also important in transferring developmental biology data into the field of applied sciences.

Estimation of the Postmortem Interval Through the Use of Development Time of Two South American Species of Forensic Importance of the Genus Lucilia (Diptera: Calliphoridae).

Obtaining the specific development time of each species of forensic interest is crucial for the estimation of an accurate and reliable Minimum Postmortem Interval (PMImin). In Argentina, Lucilia ochricornis (Wiedemann) and Lucilia purpurascens (Walker) (Diptera: Calliphoridae) were masked under the name Lucilia cluvia (Walker) for a long time still in forensic expertise. For this reason, the objective of this work is to deepen the study of the development time of these species and utilize this relevant information in the generation of different associated methods that can be used in forensics to estimate the PMI. Immature stages of L. ochricornis and L. purpurascens were reared in a brood chamber according to the following temperature treatments: 13.4, 15.1, 22.3, and 23.6°C. The development time of each stage/state of these flies was recorded as well as the resulting accumulated degree-hours (ADH), to build isomorphen diagrams and thermal summation models for each species. The development time and ADH were different between both species and their development stages. On the other hand, the methods provided for estimating PMImin provide the forensic entomologist more tools to reach accurate and reliable estimates.

Decomposition of Kemp’s ridley (Lepidochelys kempii) and green (Chelonia mydas) sea turtle carcasses and its application to backtrack modeling of beach strandings

When a sea turtle dies, it typically sinks to the bottom, begins decomposing, and floats to the surface once sufficient internal gases have accumulated to produce positive buoyancy. This process is poorly characterized and is essential to understanding where and when sea turtles found on shore may have died. We conducted decomposition studies with detailed time-temperature histories using carcasses of cold-stunned sea turtles (22 Kemp’s ridleys Lepidochelys kempii and 15 green sea turtles Chelonia mydas) at temperatures of 14-32°C and depths of 2.2-9.5 m. We found strong depth/pressure-related effects; carcasses took longer to float when incubated at greater depths than shallower depths at similar temperatures. Furthermore, carcasses incubated at colder temperatures (~15°C) took 8 times longer to float than those at 32°C at the same depth. We applied accumulated degree hours (ADH; hourly sum of ambient temperatures a carcass experienced) to characterize environmental conditions associated with different stages of decomposition and key events, including buoyancy and sinking. A formula for temperature-correction of ADH was calculated to fit a non-linear increase in decomposition at higher temperatures. These data were then used to improve an existing backtracking model by incorporating water temperature, depth (pressure), bathymetry, and postmortem condition. Heat maps of the probable mortality locations from the model agreed well with carcass and effigy drift experiments, demonstrating the overall reliability of the enhanced model. Our method can be used to estimate at-sea locations where sea turtles found washed ashore in the northern Gulf of Mexico likely died and may help inform similar efforts in other regions.

Differential Carbon Utilization by Bacteria in the Soil Surrounding and on Swine Carcasses with Dipteran Access Delayed

Mass mortality events can saturate an environment with decomposing remains. We lack an understanding of such perturbations and the extent of disruption imposed on the local ecosystem. During such instances, normal patterns of colonization and decomposition of remains by necrophagous arthropods can be retarded resulting in delayed colonization due to the proximity of multiple corpses. Therefore, this study was initiated to investigate the impact of carcasses in close proximity with delayed arthropod access on the associated microbial metabolic community profiles and those in the soil immediately under and adjacent to the remains. Field trials were conducted during the summers of 2013 and 2014 in Texas, USA. Three groups of pig carcasses were accessed: those immediately colonized by dipteran species (i.e., primary invertebrate consumers of carrion) and those experiencing delayed dipteran access by 7 or 14 days. Meteorological data for 2013 showed that the mean temperature was 30.59 ± 7.81 °C, accumulated degree hours (ADH) was 30,131.50, and precipitation was 39.12 mm, while in 2014, the mean temperature was 29.27 ± 6.49 °C, ADH was 28,090.70, and total precipitation was 171.45 mm. Bacterial function on the remains in terms of carbon utilization was significantly different between the years as well as between carcass groups, suggesting an inter-kingdom correlation between bacteria and dipteran activity. In contrast, microbial function in the soil was inconsistent between trials, indicating stochasticity within the system, probably due to differences in abiotic factors such as temperature, ADH, and rainfall.

Development of Megaselia spiracularis (Diptera: Phoridae) at different constant temperatures.

Megaselia spiracularis Schmitz, 1938 (Diptera: Phoridae) is a pest that often appears in human living areas where it can spread pathogens. Besides, the species is of forensic value. Currently, studies focusing on the development of this species are limited. Understanding the developmental patterns of M. spiracularis, therefore, is important for controlling populations of this pest and for estimating the minimum postmortem interval (PMImin). Here, we studied the development of M. spiracularis exposed to seven constant temperatures ranging from 16 to 34°C. The developmental durations, accumulated degree hours and larval body length changes were measured. Three kinds of development models that can be used to estimate the PMImin were established, including isomorphen diagram, isomegalen diagram and thermal summation model. The duration of M. spiracularis development at 16, 19, 22, 25, 28, 31 and 34°C from egg to adult stage were 1131.1±34.5, 807.3±9.3, 529.6±1.8, 367.0±8.8, 302.4±7.0, 250.0±2.1 and 232.6±1.9h, respectively. The developmental threshold temperature and the thermal summation constant were estimated as 12.0±0.5°C and 4989.7±308.9° hours, respectively. A general model represented by a logistic equation describing how larval body length will change with the time after hatching was fit to data. The present study provides basic developmental data of M. spiracularis, which can be used for achieving better control of this noxious insect as well as for estimation of its PMImin at different temperatures.

Development of Sarcophaga dux (diptera: Sarcophagidae) at constant temperatures and differential gene expression for age estimation of the pupae.

Sarcophaga dux (Diptera: Sarcophagidae) is a necrophagous flesh fly species with potential forensic value for estimating minimum postmortem interval (PMImin). The basic developmental data and precise age estimates of the pupae are significant for PMImin estimation in forensic investigations. In the present study, we investigated the development data of that species at seven constant temperatures varying from 16°C to 34°C, including body length changes of the larve, developmental duration and accumulated degree hours of the preadults. Several reference genes for relative quantification of the differentially expressed genes (DEGs) were firstly selected and evaluated in the pupae of different ages under different temperatures. The DEGs of the insects during the pupal period at different constant temperatures (34, 25 and 16°C) were further analyzed for more precise age estimation. The results showed that the developmental durations of the preadults at 16, 19, 22, 25, 28, 31 and 34°C were 1478.6±18.3h, 726.1±15.8h, 538.5±0.9h, 394.1±9.5h, 375.6±10.8h, 284.1±7.3h, and 252.5±6.1h, respectively. The developmental threshold temperature the flies was 12.27±0.35°C, and the thermal summation constant was 5341.71±249.29° hours. The most reliable reference genes during the pupal period at different temperatures were found: GST1 and 18S rRNA for the 34°C group, GST1 and RPL49 for 25°C, and 18S rRNA and 28S rRNA for 16°C. The four differential expression genes (Hsp60, A-alpha, ARP, and RPL8) have the potential to be used for more precise age estimation of pupal S. dux. This work provides important basic developmental data and a more precise age estimation method for pupal S. dux, and improves the value of this species for PMImin estimation in forensic investigations.

Development of Hydrotaea spinigera (Diptera: Muscidae) at Constant Temperatures and Its Significance for Estimating Postmortem Interval.

Hydrotaea spinigera Stein is a necrophagous species, widely distributed in Oriental and Australasian regions. Considering that the postfeeding larvae or puparia of this species can still be found in abundance at the advanced decomposition stage or even the skeleton stage of remains, it can serve as a good supplementary indicator for estimating the minimum postmortem interval (PMImin). This could also extend the range of PMImin when the primary colonizers are no longer associated with the corpse or have emerged as adults. This study investigated the development duration, accumulated degree hours, and larval body length changes of H. spinigera at seven constant temperatures ranging from 16 to 34°C, and established three development models for estimating PMImin, including isomorphen diagram, isomegalen diagram, and thermal summation model. At 16, 19, 22, 25, 28, 31, and 34°C, the development durations of H. spinigera from egg to adult stage were 1,412.6 ± 62.9, 867.4 ± 14.9, 657.1 ± 22.9, 532.3 ± 10.1, 418.8 ± 21.3, 379.8 ± 16.6, and 340.0 ± 20.3 h, respectively. The lower developmental threshold L0 was estimated as 10.50 ± 0.20°C, and the thermal summation constant K was 7,648.83 ± 146.74 degree hours. Using regression analysis, equations were obtained modeling the change of larval body length with time after hatching at different temperatures. This study provided basic data based on the growth and development of H. spinigera for the estimation of PMImin in forensic science.

Quantification of Temperature Effect on <i>Prunus yedoensis</i> Matsum. Flowering in Gyeongnam Province of Korea

This experiment was conducted to predict the flowering time of cherry blossoms. The phenological model was used to predict the accurate flowering time, and investigate the daily temperature to calculate the chilling requirement for the flowering of Prunus yedoensis Matsum. Twigs of several decades-old trees were collected on January 3, 2010 and were kept in a 2℃ refrigerator. From January 16, 2010 onward, more twigs were collected from the same field every week. Twigs of both groups were laid in water in a 25℃ growth chamber. To determine the bud-burst date and the period required for dormancy break, the state of flower buds was observed every day. The daily maximum and minimum temperatures were also collected to calculate the accumulated degree hour of the chilling requirement until the dormancy was broken. To fined out the threshold temperature and chilling requirement for the approximate flowering date, the equation was used to set the threshold temperature from 5℃ to 9℃ at intervals of 0.1℃ and calculate chill days and anti-chill days repeatedly. The equations for calculating daily Cd and Ca, are given in Table 1 for each of the five cases. Based on this prediction model, the most optimized threshold temperatures and chilling requirements were predicted to be 5.8℃ and -116.8. The broken day of the rest was estimated to be February 17. The model, used for predicting the flowering day of Prunus yedoensis Matsum. from 2012 - 2019, showed that RMSE is 2.5 days when using the measured temperature and 4.4 days when used the average March temperature of 30 years (1980 – 2010). The results showed improvement compared with the previously announced predictions of flowering days.

Temperature-dependent development of the blow fly Chrysomya pinguis and its significance in estimating postmortem interval.

Chrysomya pinguis (Walker) (Diptera: Calliphoridae) is an endemic Asiatic blow fly species of forensic importance. Chrysomya pinguis is one of the first species to colonize a corpse, especially in high altitude areas during spring and autumn when the ambient temperature is lower. Despite its potential for forensic investigations to estimate the minimum postmortem interval (PMImin), little is known about the development of C. pinguis. In this study, C. pinguis was collected from the Yangtze River Delta region of China and reared at seven constant temperatures between 16°C and 34°C to investigate the effect of temperature on development duration, accumulated degree hours and larval body length of C. pinguis. Isomorphen and isomegalen diagrams for C. pinguis were generated using the results, and equations describing the variation in larval body length during development and the temperature-induced variation in development time were also obtained. Chrysomya pinguis can complete its life cycle at 16–34°C. The mean (±s.d.) developmental durations of C. pinguis from egg to adult at 16°C, 19°C, 22°C, 25°C, 28°C, 31°C and 34°C were 811.0 ± 3.8, 544.8 ± 2.0, 379.8 ± 1.8, 306.7 ± 2.4, 250.0 ± 2.8, 203.2 ± 2.1 and 185.3 ± 1.6 h, respectively. The mean (±s.e.) developmental threshold temperature D0 and the thermal summation constant K of the whole developmental process of C. pinguis were estimated as 10.88 ± 0.21°C and 4256.50 ± 104.50 degree hours, respectively. This study provides fundamental development data for the use of C. pinguis to estimate PMImin.

Lucilia eximia (Diptera: Calliphoridae) como indicador forense para el cálculo del intervalo post mortem en Costa Rica

Introducción: Lucilia eximia es una especie de amplia distribución geográfica en Costa Rica, cuyas poblaciones son estables durante todo el año. Las características biológicas de esta especie permiten concebirla como un potencial indicador forense para el cálculo del intervalo post mortem (IPM). El objetivo del estudio fue evaluar la aplicabilidad que podrían tener las características biológicas de poblaciones locales de L. eximia para calcular el IPM mínimo en Costa Rica mediante un modelo de acumulación de unidades térmica.Materiales y Métodos: Durante el experimento se sacrificaron mediante eutanasia dos cerdos domésticos (Sus scrofa) y se expusieron en un bosque premontano húmedo tropical. A partir de los mismos se recolectaron larvas de L. eximia a las 78, 144 y 192 horas posteriores al momento de muerte para continuar con su desarrollo en condiciones controladas. Con los datos generados se realizaron las retroproyecciones térmicas para efectuar el cálculo del IPM mínimo.Resultados: L. eximia requirió en total 7 236,50 horas grado acumulados (ADH) para culminar su ciclo vital. Los IPM mínimos calculados mediante el modelo de acumulación térmica para los tres momentos de colecta fueron 112,56; 153,60 y 104,64 horas. Únicamente el valor intermedio no presentó diferencias estadísticamente significativas con el tiempo conocido de muerte (p>0,05). Conclusiones: El modelo de acumulación térmica para el cálculo del IPM mínimo utilizando L. eximia como indicador forense brindó información precisa sobre el IPM mínimo sólo cuando se tomaron las muestras en el campo a las 144 horas, lo que perfila su utilidad para las primeras etapas de la descomposición cadavérica.

Development of Musca domestica at constant temperatures and the first case report of its application for estimating the minimum postmortem interval

Musca domestica Linnaeus, 1758 (Diptera: Muscidae) is an important cosmopolitan pest with potential forensic value. Thus, the investigation of the development of M. domestica is of vital significance both for the control of its colony and for the estimation of the minimum postmortem interval (PMImin). This study observed the development of M. domestica at seven constant temperatures in the range of 16–34°C; factors such as developmental duration, accumulated degree hours, and changes in larval body length were examined. Using these results, three developmental models that could be used for PMImin estimation were established: an isomorphen diagram, an isomegalen diagram, and a thermal summation model. The mean (±SD) developmental durations of M. domestica from egg to adult at 16, 19, 22, 25, 28, 31, and 34°C were 884.6±7.4, 627.2±23.0, 437.5±11.0, 297.0±8.8, 226.4±6.3, 190.4±4.2, and 155.3±5.5h, respectively. The mean (±SE) developmental threshold temperature D0 and the thermal summation constant K were determined as 12.42±0.64°C and 3658.9±301.3 degree hours, respectively. Using regression analysis, we obtained equations that model the change in larval body length with time after hatching and change in time after hatching with larval body length. Based on the developmental data obtained, we successfully utilized the development of M. domestica to estimate PMImin for the first time.

Development of Chrysomya megacephala at constant temperatures within its colony range in Yangtze River Delta region of China

ABSTRACTChrysomya megacephala (Fabricius, 1794) is the most abundant and predominant species which arrives and colonizes a cadaver first in most parts of China. Therefore, its growth and development patterns have great implications in the estimation of the minimum postmortem interval (PMImin). In this study, C. megacephala was collected from the Yangtze River Delta region and reared at seven constant temperatures ranging from 16 °C to 34 °C. The developmental duration and accumulated degree hours, larval body length and morphological changes of C. megacephala were examined. Furthermore, we constructed three developmental models, isomorphen diagram, isomegalen diagram and thermal summation model, which can be used for estimating PMImin. The developmental durations of C. megacephala at 16 °C, 19 °C, 22 °C, 25 °C, 28 °C, 31 °C and 34 °C are (794.8 ± 14.7), (533.2 ± 10.1), (377.8 ± 16.8), (280.8 ± 15.1), (218.9 ± 8.5), (190.8 ± 10.1) and (171.8 ± 6.8) h, respectively. The developmental threshold temperature D0 is (11.41 ± 0.32) °C, and the thermal summation constant K is (3 418.7 ± 137.0) degree hours. Regression analysis was conducted to obtain equations of the variation in larval body length with time after hatching, and variation in time after hatching with body length. Moreover, our study divides the intra-puparial morphological changes of C. megacephala into 11 sub-stages, and provides the time range experienced by each sub-stage. The results of this study provide fundamental development data for the use of C. megacephala in PMImin estimations.

Postmortem interval estimation based on Chrysomya albiceps (Diptera, Calliphoridae) in a forensic case in the Andean Amazon, Caquetá, Colombia

ABSTRACT This is the first application of forensic entomology in a case involving a human corpse found in the urban area of the Municipality of Florencia, Caquetá, Colombia, in the Piedemont of the Colombian Amazon. Three days after removing the body from the scene, pupae and puparia were collected and identified as Chrysomya albiceps (Wiedemann, 1819) (Diptera, Calliphoridae). The postmortem interval was estimated on the basis of previously published data and verified through accumulated degree hours (ADH) and intrapuparial development. The estimated minimum postmortem interval was of 229 hours (9.5 days).

Photophase Duration Affects Immature Black Soldier Fly (Diptera: Stratiomyidae) Development.

This study tested the effect of photophase duration on black soldier fly, Hermetia illucens (L.; Diptera: Stratiomyidae), development. Successful larval eclosion, development time and adult emergence were measured for individuals exposed to 0 h, 8 h, and 12 h of light, at approximately 27°C and 70% relative humidity. Accumulated degree hours (ADH) were calculated to correct for differences in temperature across treatments. Larvae successfully eclosed in all treatments, with larvae in 12 h light requiring 5.77% and 4.5% fewer ADH to eclose than larvae in 0 h and 8 h, respectively. Overall, larvae in 0 h required 39.34% and 37.78% more ADH to complete their development from egg to adult than larvae in 8 h and 12 h, respectively. The effect of photophase duration on juvenile development was largest in the post-feeding stage, and smallest in the pupal stage. Specifically, post-feeding larvae in 0 h required 80.02% and 90.08% more ADH to pupate than larvae in 8 h and 12 h, respectively, but pupae in 8 h required 9.63% and 7.52% fewer ADH to eclose than pupae in 0 h and 12 h, respectively. Lastly, larval mortality was significantly higher in 0 h, with 72% survivorship, and 96% and 97% in 8 h and 12 h, respectively. However, 17.8% of mortality in the absence of light is hypothesized to be a result of predation by Arachnidae and Blattidae. These data could prove valuable for optimizing industrial processes for mass-production of this species for use as alternative protein in feed for livestock, poultry, and aquaculture.

A Statistical Method to Construct Confidence Sets on Carrion Insect Age from Development Stage

The age of a carrion insect associated with a corpse may represent a minimum postmortem interval. No method has been proposed before for constructing a confidence set on age based on development stage modeled as a categorical response. This paper illustrates the application of exact p values, first developed for succession data, to construct a confidence set on a carrion insect’s age based only on its development stage. It uses published development data for Lucilia sericata, with individuals reared at different temperatures pooled into sets of similar age as indexed in accumulated degree hours. Rates of coverage of true ages, assessed using each insect as a singleton holdout sample, were greater than the nominal 95% level.

Post-Colonization Interval Estimates Using Multi-Species Calliphoridae Larval Masses and Spatially Distinct Temperature Data Sets: A Case Study.

Common forensic entomology practice has been to collect the largest Diptera larvae from a scene and use published developmental data, with temperature data from the nearest weather station, to estimate larval development time and post-colonization intervals (PCIs). To evaluate the accuracy of PCI estimates among Calliphoridae species and spatially distinct temperature sources, larval communities and ambient air temperature were collected at replicate swine carcasses (N = 6) throughout decomposition. Expected accumulated degree hours (ADH) associated with Cochliomyia macellaria and Phormia regina third instars (presence and length) were calculated using published developmental data sets. Actual ADH ranges were calculated using temperatures recorded from multiple sources at varying distances (0.90 m–7.61 km) from the study carcasses: individual temperature loggers at each carcass, a local weather station, and a regional weather station. Third instars greatly varied in length and abundance. The expected ADH range for each species successfully encompassed the average actual ADH for each temperature source, but overall under-represented the range. For both calliphorid species, weather station data were associated with more accurate PCI estimates than temperature loggers associated with each carcass. These results provide an important step towards improving entomological evidence collection and analysis techniques, and developing forensic error rates.

Case Study and PMI Estimation of Male Corpse from Ludhiana, Punjab, India: An Implication of ADH Method

Forensic entomology is the study of how insects consume decomposing human remains and provide data which can aid medical/legal investigations. Common questions answered through the use of forensic entomology include time since death, movement of a body from one location to another, determination of environmental conditions to which a body has been exposed, location of traumatic wound sites, identification of toxicological deaths, and location of drug trafficking. Present case study deals with the estimation of Postmortem interval (PMI) by using Accumulated degree hour (ADH) method. 45 years old male corpse was recovered from house in residential area of Ludhiana, Punjab, India on 5 April 2015. Wounds resulting from sharp-edge weapon were found on the head. Numerous second instar larvae were collected from the body. The larvae were reared and identified as Chrysomya megacephala (Fabricius). Temperature and humidity data was taken from Meterological Department of Punjabi University, Patiala.

Heat-induced mass mortality of invasive zebra mussels (Dreissena polymorpha) at sublethal water temperatures

We observed a massive die-off of zebra mussels (Dreissena polymorpha) on the epilimnetic sediments of Gull Lake (Michigan, USA) during the relatively warm summer of 2010, even though water temperatures were below widely reported lethal temperatures of ≥30 °C. We followed up this observation with 4 years of in situ monitoring of caged mussels stocked across a depth–temperature gradient in Gull Lake. Mortality of caged D. polymorpha was largely explained by accumulated degree hours >25 °C, a temperature threshold that is considerably lower than laboratory-derived lethal temperatures for D. polymorpha. We also assessed both the acute and chronic thermal tolerance of Gull Lake D. polymorpha with laboratory experiments, which confirmed higher acute tolerance (up to 32 °C) under otherwise ideal conditions but high susceptibility to prolonged exposure to “sublethal” temperatures (exceeding 1700 degree hours >25 °C) as occurred in Gull Lake during the die-off. Our results indicate that the thermal tolerance of D. polymorpha under natural conditions may be lower than has been reported from laboratory studies. Lower temperature tolerance may have major implications for the dynamics, impacts, and management of this invasive species given future climate change scenarios.