Chronobiological Effect on the Reproductive Behavior of Chrysomya megacephala (Diptera: Calliphoridae)

The most widely used entomological method of determining the time since death (minimum postmortem interval, mPMI) has been calculating the developmental time of blow flies (Diptera: Calliphoridae) on the deceased body. However, because blow flies are known to be diurnal, nocturnal oviposition has been excluded from standard mPMI calculations. This has been challenged by recent studies demonstrating nocturnal oviposition due to an unknown reason. Therefore, this study investigated the role of chronobiology. We recorded the locomotion amount and pattern of Chrysomya megacephala (Fabricius, 1794) (Diptera: Calliphoridae) under different chronobiological conditions and examined whether Ch. megacephala can oviposit under nighttime conditions in field and laboratory settings. Subjects were found to have a daily activity pattern under normal darkness conditions (12:12 L:D) and under continuous darkness (DD), but they exhibited no pattern under continuous light (LL). Free-running period was approximately 1,341 min/d (22.35 h/d). In the field, no flies were observed during nighttime. Oviposition occurred in the laboratory setting during daytime with no lights and during nighttime with artificial lights. Free-running subjects oviposited in both active and resting periods, with more eggs laid during active than resting periods. The result of this study indicates it is possible to induce oviposition behavior during evening hours on Ch. megacephala. However, this was only observed in the laboratory setting and could only happen during the flies’ subjective day.

Efeito da contaminação por inseticida tiametoxam sobre o comportamento da mosca de interesse forense Chrysomya megacephala (Fabricius)

Muitos fatores podem interferir na estimativa do Intervalo Pós-Morte (IPM) que é o tempo entre a morte e o achado de corpo, dentre eles substâncias que alteram os padrões de desenvolvimento dos insetos colonizadores de carcaças. Neste estudo testamos a hipótese de que, se um recurso simulando um cadáver estiver contaminado pelo inseticida tiametoxam, moscas varejeiras da espécie Chrysomya megacephala (Fabricius) (Diptera: Calliphoridae) irão evitar explorá-lo e consumi-lo. Foram feitos testes de dupla escolha nos quais as moscas podiam optar por recurso contaminado ou não contaminado. Os resultados mostraram que estas moscas varejeiras não evitam carne contaminada com inseticida e, além disso consomem o recurso, contudo, ao fazerem isso executam comportamentos atípicos, como expor o ovipositor, e limpar-se frequentemente. Estes resultados sugerem que caso um cadáver seja contaminado com o inseticida tiametoxam, as moscas irão explorá-lo como recurso, no entanto, como esse produto altera o seu comportamento, seu ciclo de vida possivelmente será alterado, bem como a ordem de chegada das espécies, o que poderá afetar a estimativa do IPM, tendo importante impacto sobre as perícias forenses.

Initial Work on Sex-Specific Growth Curve Guidelines for Forensically Important Blow Flies Using Chrysomya megacephala (Diptera: Calliphoridae) Entire Age Cohorts

Sex is a factor influencing development in many insect species, but is not widely studied in forensically important blow flies. If sex influences blow fly development, knowing the sex of a larva from a corpse can increase precision in estimates of that larva’s age. The improved prediction of larval age will make estimates of time since death using entomological evidence better. Larvae lack sexually dimorphic morphological characteristics, so sex is not immediately known visually. To generate sexually dimorphic reference growth curves, a subsample must be large enough to ensure enough males and females are present for comparison. Using two entire age Chrysomya megacephala (Fabricius) cohorts, we evaluated the minimum sample number needed to have enough individuals of both sexes for comparison using 95% prediction intervals. Through a simulation of three trials of 1000 random replicates, we determined that a sample size of 19 would prevent any instance of a comparison not occurring because of insufficient sampling from one sex. As the current method for molecular sex determination can be expensive, we also compared how the results of various subsampling percentages compare those of the entire age cohorts. We found that subsampling at least 50% of an entire cohort leads to almost identical results in comparison to the entire age cohort. Together, these findings will help establish guidelines for generating sex-specific reference growth curves. A uniform approach to generating these sex-specific growth curves will lead to more consistency in age estimates made from them.

Muscidae e Calliphoridae (Diptera, Brachycera) associados à decomposição cadavérica no noroeste do Paraná

O presente trabalho teve como objetivo listar quais são os dípteros necrófagos na região noroeste do Paraná. As informações fazem parte de um projeto, aprovado no comitê de ética em pesquisa de animais, em desenvolvimento no IFPR Campus Umuarama. Durante o estudo, um cadáver de suíno com o peso aproximado de 10 kg foi utilizado como substrato, o qual foi colocado em uma gaiola com uma tela, para impedir a entrada de vertebrados necrófagos. A coleta dos insetos foi realizada por meio de uma armadilha modificada. A gaiola de metal que continha o substrato estava fixada no terreno do IFPR Campus Umuarama. Em relação aos insetos foram coletadas cinco espécies de Muscidae (Sarcopromusca pruna; Musca domestica; Hydrotaea aenescens; Sythesiomyia nudiseta e Stomoxys calcitrans) e seis espécies de Calliphoridae (Cochliomyia macellaria; Chrysomya albiceps; Chrysomya megacephala; Lucilia eximia; Lucilia cuprina e Hemilucilia segmentaria). Os espécimes de Stomoxys calcitrans podem ter sido coletados devido à presença de gado de corte próximo ao local. O processo de decomposição se completou em seis dias, o que pode ser devido aos altos índices de temperatura e baixos índices de umidade observados no local. Nesse período foram observados quatro estágios: fresco; enfisematoso; coliquativo e esqueletização. Estes dados são importantes para a construção de um banco de dados de espécies de importância forense.

Study of the bioecology of Chrysomya (Robineau-Desvoidy, 1830) (Diptera: Calliphoridae): Collections

The Chrysomya primary importance to the field of medico legal Forensic Entomology is due to the genus' predictable life cycle length, allowing researchers to accurately estimate a postmortem interval. The aim of this study was to carry out a bibliographical summary on the blowflies of the genus Chrysomya (Insecta: Calliphoridae) with emphasis on the species: Chrysomya albiceps (Wiedemann, 1819) (Diptera: Calliphoridae), Chrysomya megacephala, (Fabricius, 1794) (Diptera: Calliphoridae) and Chrysomya putoria (Wiedemann, 1830). The mini review consists of bibliographical research on the muscoid dipterans (Muscomorpha) (Order: Diptera). The research was carried out in studies related to quantitative aspects of the Family and Species (taxonomic groups) and in conceptual aspects such as origin, geographic distribution, biology, life cycle, as a secondary vector of enterobacteria, for causing secondary myiasis and importance in Forensic Emtomology. A literature search was carried out containing articles published from 1971 to 2021. The mini review was prepared in Goiânia, Goiás, from August to September 2021, through the Online Scientific Library (Scielo) and internet. This is a family of blowflies of great ecological and medical-sanitary importance, as they are decomposers of organic matter, with their larvae usually developing in decayed material of animal origin, decomposing it and quickly consuming the carcasses, thus removing possible sources of diseases and recycling nutrients.

Terapia larval: protocolo básico de manutenção, desinfecção, transporte e aplicação de larvas de Chrysomya megacephala (Fabricius, 1794) (Diptera: Calliphoridae)

Chrysomya megacephala (Fabricius, 1794) (Diptera: Calliphoridae) is an exotic blowfly in Brazil and it is considered one of the main species of medical-forensic importance. Their larvae have a necrophagous habit with a high forensic potential and they are also considered an important tool for treating chronic wounds, a technique known as maggot therapy, which is not yet routinely used in Brazil despite proven efficacy. In this context, the present work aims to describe a protocol for carrying out the technique, with the complete description of colony maintenance, preparation and disinfection of eggs, packing and transportation of larvae for use, application and removal of the larvae on patients. Thus, with this protocol, the maggot therapy can be disseminated and performed by other research groups.