Technical Note: A comparison of solvents for optimal extraction and morphological identification of blow flies (Diptera: Calliphoridae) from sticky traps

Passive sampling techniques such as sticky traps are recommended for research studies assessing colonisation patterns of forensically important flies. However, there are no standardised protocols for the optimal removal of flies to ensure accurate morphological identification to species level. This study assessed the use of four freely available solvents (mineral oil, vegetable oil, baby oil and an orange-based solvent) in terms of facilitating extraction from sticky traps, and potential effects on subsequent identification of three blow fly species of forensic importance, Calliphora vicina, Calliphora vomitoria and Lucilia sericata. Results indicated that species were differentially affected by the oils but, overall, the orange-based solvent had the least effect on the morphological features of each species, and therefore, was considered the best throughout the study. Additionally, the orientation of flies on the traps had no significant effect on the quality of morphological characteristics. It is recommended that the orange-based solvent method outlined in this paper is used for the removal of blow flies from sticky traps.