Forensic Entomology Calliphoridae or Blow Flies

Question: Discuss about theForensic Entomologyfor Calliphoridae or Blow Flies. Answer: Introduction It is believed that forensically significant Calliphoridae or blow flies are not active nocturnally and do not oviposit in the dark (Mohr, Tomberlin, 2014). However, Barnes, Grace, Bulling, (2015) demonstrated that blow flies lay eggs at night and also artificial lighting stimulates the daylight hours. The fly biologists illustrated that flies in the outdoor are not much active and do not lay eggs at night. Diurnal activity graph demonstrates low movement towards bait during early daylight, peak at afternoon and steep decline towards late afternoon. Whether or not the Calliphoridae flies nocturnally oviposit, is one of the major estimable factors of time since death that is used as entomological evidence. This write-up would strive to explore a debate on the ability of the blowflies to oviposit in the dark and at night and their nocturnal activity by considering recent journals that focus on the same. Based on Greenbergs experiment, who asserted that blow flies lay eggs at night, Singh and Bharti (2001) further carried out an experiment to support this hypothesis. They have used frozen mutton pieces as medium and checked for maggots during March and September, irrespective of the time of the days. It was shown that day time also attracted the blow flies in terms of oviposition. The researchers have carried out a 14night trial, where oviposition took place in five incidences and matched with the Greenbergs data. This indicates their willingness to through some light on the choice of oviposition medium by the Calliphoridae and further provided a scope to investigate association between chances of oviposition by the Calliphoridae and light intensity at night. On the other hand, Zurawski et al., (2009) investigated the nocturnal oviposition by the blow flies with regard to sunset and sunrise, evaluated abiotic variables that might affect the oviposition by the blow flies and conducted a series of laboratory experiments in order to test the activity of the blow flies under darkness. The researchers have placed pig carcasses in the field 2 hours after the sunset and observations were made hourly in the next morning. They have observed no oviposition at night. Even, while they have carried out a laboratory experiment in dark room by placing liver of the pig carcases on the ground or kept in hanging position no flies could fly. This study not only showed that the blow flies do not oviposit at night but also demonstrated that the possibility of nocturnal oviposition in dark and on pig carcasses is extremely low. Thus, this experiment supports the long standing notion that blow-flies are nocturnally inactive and do not oviposit in the dark. Howe ver, factor like pig carcasses raises a concern, if the flies actually do not lay eggs in the dark or do not oviposit on pig carcasses. Amendt, Zehner Reckel, (2008) carried out field experiments and indoor experiment to evaluate nocturnal egg laying behaviour of the Calliphoridae. For field experiment, two different types of attraction were used: fresh liver of the beef and dead hedgehogs, which were kept at different rural and urban location. For indoor experiment, liver was kept in plastic bags containing fly females. No oviposition was observed at night in the field, where the temperature was within 10-24c but nocturnal oviposition took place in darkness within plastic boxes, where temperature was set at 25c. It was concluded by the researchers that the blow flies are unlikely to oviposit under normal condition, but takes place at certain situation like uncertain increase of night temperature. Similarly, Wooldridge, Scrase, Wall, (2007) demonstrated that light intensity is an exogenous stimulus responsible for the nocturnal activities of the blow flies. Though liver odour increases the activity of the blow flies, it is not an active stimulus. So, it could be mentioned that blow fly activity can be directly modulated by the intensity of the light without any requirement for any volatile odour in order to start activation. Activity of the blow flies, irrespective of the absence or presence of liver bait also indicates that the variation in the activity level of the flies is not causally associated with how they respond to various odours. Zulaikha, Zuha, (2016) demonstrated Megaselia scalaris (fly) are active and can oviposit during night and day times. So, exposure to light did not affect the egg laying activities during nocturnal and diurnal periods. This indicates a need to consider nocturnal oviposition while flies are considered as reference for the estimation of PMI. Oviposition termination at night has forensic importance as it might alter the estimation of the PMI duration. Thus, if fly eggs are identified in a dead body during early morning or night, one could reach to a conclusion on when the death has been occurred (earlier or previous day). Different insect species could fly in low light intensity or at night. The selected topic aims to evaluate whether blow flies are able to be active at night and lay eggs in dark. The above discussion pinpoints that various theories are present that support and oppose the long standing belief that the blow-flies are not nocturnally active and do not lay eggs in the dark. Various factors (intensity of light, temperature, position of the bait, odour and so on) are responsible for stimulating the nocturnal activity and oviposition, but there was no literature available that focus precisely on all the responsible factors, which actually creates a gap. Age of the fly larvae is used to evaluate the minimum PMI in forensic entomology. So, the understanding of the factors, which probably delay the time between oviposition and death are of utmost importance. One of such factors in this context is the effects of darkness period. Majority of the blow flies are through to be diurnal and comparati vely inactive during the night. So, baits that are kept at night would not attract blow flies till the morning. Nevertheless, various informal observations have suggested that nocturnal oviposition could take place in certain species of blow flies, Calliphora vicina is a prominent example in this context. References Amendt, J., Zehner, R., Reckel, F. (2008). The nocturnal oviposition behaviour of blowflies (Diptera: Calliphoridae) in Central Europe and its forensic implications.Forensic Science International,175(1), 61-64. https://dx.doi.org/10.1016/j.forsciint.2007.05.010 Barnes, K. M., Grace, K. A., Bulling, M. T. (2015). Nocturnal oviposition behavior of forensically important diptera in Central England.Journal of forensic sciences,60(6), 1601-1604. Greenberg, B. (1990). Nocturnal Oviposition Behavior of Blow Flies (Diptera: Calliphoridae).Journal Of Medical Entomology,27(5), 807-810. https://dx.doi.org/10.1093/jmedent/27.5.807 Mohr, R. M., Tomberlin, J. K. (2014). Environmental factors affecting early carcass attendance by four species of blow flies (Diptera: Calliphoridae) in Texas.Journal of medical entomology,51(3), 702-708. Singh, Bharti, M. (2016). further observations on the nocturnal oviposition behaviour of blowflies (Diptera: Calliphoridae ).Forensic Science International,120(2001), 124-126. Wooldridge, J., Scrase, L., Wall, R. (2007). Flight activity of the blowflies, Calliphora vomitoria and Lucilia sericata, in the dark.Forensic Science International,172(2-3), 94-97. https://dx.doi.org/10.1016/j.forsciint.2006.12.011 Zulaikha, A. S., Zuha, R. M. (2016). Nocturnal oviposition of the forensic scuttle fly, Megaselia scalaris (Loew)(Diptera: Phoridae), indoors.Egyptian Journal of Forensic Sciences. Zurawski, K. N., Benbow, M. E., Miller, J. R., Merritt, R. W. (2009). Examination of nocturnal blow fly (Diptera: Calliphoridae) oviposition on pig carcasses in mid-Michigan.Journal of medical entomology,46(3), 671-679.