The occurrence of stalk-eyed flies (Diptera, Diopsidae) in the Arabian Peninsula, with a review of cluster formation in the Diopsidae

Catalogue and distribution data are presented for the six Diopsidae species known to occur in the Arabian Peninsula: Sphyracephala beccarii, Chaetodiopsis meigenii, Diasemopsis aethiopica, Diopsis arabica, Diopsis mayae and Diopsis sp. (ichneumonea species group). The biogeographical aspects of their distribution are discussed. Records of Diopsis apicalis and Diopsis collaris are removed from the list for Arabia as these were based on misidentifications. Synonymies involving Diasemopsis aethiopica and Diasemopsis varians are discussed. Only one out of four specimens in the D. elegantula type series proved conspecific with D. aethiopica. The synonymy of D. aethiopica and D. varians is rejected. A lectotype for Diasemopsis elegantula is now designated. D. elegantula is proposed as junior synonym of D. varians. A fly cluster of more than 80,000 Sphyracephala beccarii, observed in Oman, is described. The occurrence of cluster formations in the Diopsidae is reviewed, while a possible explanation is indicated.