Effects of population variations and temperature on Chrysomya megacephala (Diptera: Calliphoridae) development: implications for estimating the postmortem interval.

Forensic entomology requires knowledge of the developmental rates of the species that colonize a body after death to estimate the postmortem interval (PMI). These developmental rates may vary depending not only on the species but also on the geographic location due to population differences. Therefore, the objectives of this work were to determine the developmental duration of the forensically important fly Chrysomya megacephala under constant controlled and field condition temperatures and to compare these results, through a meta-analysis, with data reported by other authors on populations from different localities. For this, C. megacephala colonies were established in the laboratory, and the duration of the life cycle was studied at two controlled temperatures (25 °C and 27 °C) and field conditions (27.5 ± 3.2 °C). Analysis of variance was performed to determine differences in developmental time and larval length between constant laboratory temperatures and field conditions. A generalized linear model was performed with predictor variables extracted from the literature (diet, relative humidity, latitude, longitude) to evaluate the effect of population variation on developmental times. The results showed significant differences in developmental times between 25 and 27 °C. As expected, the complete life cycle of C. megacephala was shorter at 27 °C. Finally, the meta-analysis suggested differences between the developmental times of different populations, based on temperature and geographic location. The results of this study provide fundamental developmental data to use C. megacephala in PMI estimations. Finally, we suggest that, when making expert reports, information from local populations should be used to determine a more accurate and reliable PMI.

Life Cycle of Chrysomya rufifacies (Diptera: Calliphoridae) Under Semi-Controlled Laboratory Conditions.

Adult Calliphoridae flies, as well as their immature stages collected from carcasses, have been used as evidence in forensic investigations to estimate the postmortem interval (PMI), particularly those of the genus Chrysomya as it is one of the first genera to colonize a corpse. Chrysomya rufifacies (Macquart 1842), due to its appearance in cadaveric remains, plays a fundamental role in the study of forensic entomology. For this reason, we determined the biological cycle of C. rufifacies under semicontrolled laboratory conditions: uncontrolled average fluctuating temperature of 29. 76 ± 3. 22°C, uncontrolled average fluctuating humidity of 48. 91 ± 11.13%, and a controlled photoperiod of 12/12 (L/O). We established that the total development time from oviposition to adult emergence of C. rufifacies was 6. 5 d. The eggs took 12 h to hatch after oviposition. The complete larval stage took 60 h (instar 1 = 12 h, instar 2 = 12 h, instar 3 = 24 h, instar 3 post-feeding = 12 h). The pupa had a duration of 84 h. The species needed a total of 4642.8(±4.59) accumulated degree-hours (ADH) to complete its biological cycle.

Flesh Flies (Diptera: Sarcophagidae) Attracted to a Snake Carcass (Boa constrictor) in Yucatan Peninsula, Mexico.

A study was carried out to determine Sarcophagidae diversity attracted to the different stages of decomposition of a Boa constrictor cadaver during late winter in the Yucatan Peninsula. As a result of this study, seven species of Sarcophagidae were documented, Oxysarcodexia conclausa (Walker, 1861) (Diptera: Sarcophagidae), Peckia (Euboettcheria) volucris (Wulp, 1895) (Diptera: Sarcophagidae), Blaesoxipha (Gigantotheca) plinthopyga (Wiedemann, 1830) (Diptera: Sarcophagidae), Oxysarcodexia amorosa (Schiner, 1868) (Diptera: Sarcophagidae), Ravinia derelicta (Walker, 1853) (Diptera: Sarcophagidae), Ravinia effrenata (Walker, 1861) (Diptera: Sarcophagidae), and Titanogrypa (Cucullomyia) placida (Aldrich, 1925) (Diptera: Sarcophagidae), The last five species listed are the first documentation of their presence in the Yucatan Peninsula in Mexico. Sarcophagids were present throughout the decomposition process; however, the greatest abundance and diversity of this family were present during the advanced decay stage. This is the first work on flesh flies in the region and the first in the country that has focused on wildlife.

Laboratory development and field validation of Phormia regina (Diptera: Calliphoridae).

Immature blow flies (Diptera: Calliphoridae) collected from decomposing human remains are often used to determine the minimum postmortem interval (PMImin). Phormia regina (Meigen) is a common blow fly of cosmopolitan distribution that is often associated in such cases. P. regina development at two different cyclic temperatures was examined in this study. A field validation study was conducted to determine the accuracy of applying these data to determine the PMImin. Minimal total development time was 32.52 d at cyclic 14.0 +/- 2.0 degrees C and 16.60 d at cyclic 20.5 +/- 3.1 degrees C. The minimal larval development was significantly different (P < 0.05) across temperatures. Larval development needed 15.5 d at 14.0 degrees C and 7.5 d at 20.5 degrees C. For the validation study, instar, mean, and maximum of length and weight data of the larvae collected in the field were analyzed with data generated from the 20.5 degrees C treatment, as it more closely reflected the field conditions experienced. Accuracy in estimating PMImin, was highly variable depending on the unit of measurement used and instar of P. regina collected from the field. Using the oldest instar to estimate a PMImin resulted in ranges that always encompassed the true time of colonization. Accuracy in hours when using measurements units as mean length or weight, and maximal length or weight, varied among the larval instars. In the first instar the greatest overestimation was made with maximal weight while the greatest underestimation was made with mean weight. The most accurate estimate produced with first instars was based on maximal length. In the second instar, there was no overestimation and the greatest underestimation was made with mean weight and the most accurate estimate produced was with maximal length. In the third instar, the greatest overestimation was made with maximal length, and the greatest underestimation was made with mean weight. The estimated time of colonization based on maximal weight was most accurate for third instars.