Occurrence ofMegaselia imitatrixBorgmeier andMegaselia hansonixDisney in Florida (Diptera: Phoridae)

Abstract

During a study of container-inhabiting mosquitoes in the Florida Keys, Hribar et al. (2004) reported finding larvae of a phorid fly, Megaselia scalaris (Loew), in some aquatic habitats. Identification was made on the basis of reared adults. Since that time, aquatic phorid larvae occasionally have been collected during routine mosquito surveillance. Examination of those larvae revealed that their general habitus did not conform to that of descriptions of the larva of M. scalaris. Particularly notable were the caudal spiracles being located on an extensible tube, similar to beach fly larvae (Diptera: Canacidae), and large bulbous anal gills, typical of aquatic Phoridae (Disney 1991). Some specimens were cleared and slidemounted and the cephalopharyngeal skeleton compared to illustrations of that of M. scalaris (Liu & Greenberg 1989). Cephalopharyngeal morphology was not consistent with M. scalaris; instead, larval morphology was consistent with Megaselia imitatrix Borgmeier and M. hansonix Disney (Hanson & Disney 2008; Disney et al. 2009). Attempts to rear additional larvae to the adult stage were unsuccessful. However, adult phorids were seen occasionally in traps set for adult mosquito surveillance. The Florida Keys Mosquito Control District deploys several different mosquito traps for adults. Phorids were collected in dry-ice-baited ABC light traps (Clarke Mosquito Control, Roselle, Illinois, USA) and BG Sentinel traps (Biogents, Regensburg, Germany) baited with octenol and lactic acid. Adult Phoridae were cleared and mounted on microscope slides according to the protocol of Wirth & Marston (1968). Adult males were compared with the figures and description provided by Disney et al. (2009). Four species were identified: Megaselia hansonix Disney, M. imitatrix Borgmeier, M. scalaris (Loew), and an apparently undescribed species of Megaselia. Voucher specimens of adult flies have been deposited in the Los Angeles County Museum of Natural History, California, and the Cambridge University Museum of Zoology, UK.