Morphology successfully separates third instar larvae of Muscina

Three representatives of the muscid genus Muscina Robineau-Desvoidy (Diptera: Musicidae), Muscina levida (Harris), Muscina prolapsa (Harris) and Muscina stabulans (Fallén), are well known for their medical, veterinary and forensic importance. However, data in the literature provide contradictory information for the identification of third instar larvae of these species. This hinders easy species differentiation because it requires the rearing of material to adult stages in order to facilitate reliable identification. Third instar larvae of these three Muscina species were studied in detail using light and scanning electron microscopy to provide thorough redescriptions of their morphology. Existing information concerning third instar morphology, with particular reference to its value for taxonomy and identification, is revised and discussed. Emden's spiracular distance factor (SDF) is considered here as inappropriate for identification purposes in third instar larvae of Muscina spp. because its values are not constant ratios but increase during larval maturation and overlap in the examined species. These species were, instead, discriminated here by differences in the spinulation patterns of their abdominal segments.