INSECTA. 585 



sess. These are termed Stratiomydae, and include the ge- 

 nera Stratioinys, Oxycera, and Nemotelus, 



In the remaining families, with a univalvular sheath^ 

 the proboscis is always more or less protuberant. Among 

 these, there are some which resemble the preceding fami- 

 lies, in having only three joints in the antennae. The Co- 

 nopsidag have the sheath bent, and the sucker, with two 

 filaments, as Conops, Zodion, Homoxis, Bucentes, and 

 Myopa. The Bombylidae have the sucker composed of 

 from four to six filaments, and the sheath is destitute of 

 large lips, as Bombylus, Ploas, Mithrax, Nemestrina, Pa- 

 nops, Cyrtus, Acrocera, Astomella ; together with Empis, 

 Asilus, and Dioctria. The Tabanidse have the sheath fur- 

 nished with large lips, and the third joint of the antennie 

 distinctly annulated ; as in Tabanus, Pangonia, and Cae- 

 nomya ; together with Pachystoma, Rhagis, Dolechopus, 

 and Mydas. Others have six joints or more in the an- 

 tennae. Among these the Bibionidse have moniJiform or 

 perfoliated joints, about the length of the head, as Bibio, 

 Scathopsis, and Simulium. The Tipuladae have filiform or 

 setaceous antennae, as Tipula, Cetenophora, Trichocera, 

 Psychoda, Tanypus, Limonia, Hexatoma, and Culex, all 

 of which are destitute of ocelli ; together with Asindulum, 

 Ceroplatus, Mycetophila, and Rhyphus, which are fur- 

 nished with ocelli. 



In the remaining genera of this class, the sheath of the 

 sucker is bivalve. The Hypoboscidae have the head distinct- 

 ly divided from the thorax, as in Hippobosca, Feronia, Or- 

 nithomyia, Craterina, Oxypterum, and Melophagus. In 

 the genus Nycteribia, the head is united with the thorax. 



Order IV.— Aptera. 

 Into this class we have placed tribes of insects which 

 differ greatly from each other in the organs of digestion ; 



