Mobile maggots: Lucilia sericata (Diptera: Calliphoridae) larval growth and mortality rates associated with movement between food substrates

Lucilia sericata (Diptera: Calliphoridae) is one of the most commonly studied blow fly species in forensic science and is often used in human death investigations when estimating postmortem interval (PMI). To assist in PMI estimations, maggots from a scene are transferred from the remains to a protein source (i.e. beef liver) in the lab. The maggots are reared into adults and identified to species. However, transferring maggots from their original substrate to a new substrate can cause a delay in feeding and growth, resulting in smaller larvae and higher mortality. These delays can make it difficult to accurately determine species’ age and estimate PMI and very little work has been done showing why or when species will stop feeding after a substrate transfer. Thus, we conducted a series of experiments to determine when maggots could be transferred between substrates without interrupting growth and development.

Fifty Lucilia sericata eggs (collected within 30 minutes of oviposition) were placed on a moist paper towel square in a 147 mL cup with 12.5 g of beef liver. The cup was placed on 2.5 cm of untreated pine shavings in a 750 mL container. The container was placed in a rearing chamber at 25 ºC with a light:dark cycle of 16:8. After the eggs hatched, maggots were transferred to different substrates (new beef liver and previously fed-on beef liver). Measurements were taken at three points: 1^st-2^nd stage, 2^nd-3^rd stage, and 3^rd-3^rd migratory stage, and were replicated four times. Controls consisted of maggots allowed to complete development without being moved.

Our results illustrate the importance of growth and development and how they can be altered due to substrate movement. This knowledge can improve PMI estimations through more accurate development times and a better understanding of maggot biology.