Building an informed identification key for Dixa (Diptera: Dixidae) larvae

Dixidae (Diptera: Culicomorpha) is an obscure family of mosquito-like flies known for their cosmopolitan distribution and association with freshwater habitats. Although their charismatic larvae are well known at the level of family, there is a dearth of information about larvae at the species level. In fact, less than 10% of the world’s dixid species are known from the larval stage. Recent efforts to collect and associate larvae of Nearctic dixid species, largely through DNA fingerprinting, to name-bearing adults have allowed great strides to be made in the discovery and documentation of morphological diversity present. For this presentation, we present results from our studies upon Dixa Meigen and Meringodixa Nowell. A major goal of this study is the creation of dichotomous keys useful for separating larvae of all Nearctic species, thus allowing further study of their ecology, life history, and distribution. Briefly, our workflow is as follows: (1) high-resolution images of larvae are captured and stacked using a high-end Leica stereomicroscope; (2) images are optimized using Adobe Photoshop; (3) photographed larvae are subjected to a non-destructive DNA extraction method (yielding an intact voucher specimen) to generate DNA barcodes; (4) larval DNA barcodes are matched to ones generated from known specimens, typically adult males. The resulting figures are accompanied by formal written descriptions from which the dichotomous keys are generated. Our results reveal that larvae are often distinguishable to the level of species.