86 EMPID^E. 



stoma muticum. Proboscis mento recondite. Alae lobo axillari 

 obsolete ; areola brachiali utraque completa ; anali a margine posteriore 

 distante, nonnunquam obsoleta ; venis externo-mediis binis aut ternis. 

 Abdomen segmentis septem (aut ultra). 



Although this family seems sufficiently defined by the essential 

 characters, it is not easy to give a more extended description 

 that will be applicable generally, so many are the modifications 

 of the secondary characters. They are generally small insects, 

 and rather slender : the head more or less globose, and usually 

 much narrower than the thorax : the vertex not impressed ; the 

 front narrow, sometimes entirely occupied by the eyes meeting 

 above the anteniiee ; the epistoma without moustache or bristles, 

 and without a defined orbit : the cheeks vary. The proboscis is 

 often long, and usually rigid, the pointed horny labrum being the 

 most conspicuous part : the development of the other organs 

 varies ; the maxillae at first being found almost as well developed 

 as in the BombyUda, and bearing the palpi attached to their base 

 (Empis, &c.) ; but in the greater number of genera the maxillae 

 become obsolete, and even where small rudiments of them remain, 

 as in Hybos, the palpi are detached from them and inserted at 

 the sides of the mentum.'* The palpi are usually of one piece, 

 rarely presenting another small joint at the base ; their propor- 

 tions, form, and direction vary.f The antennae are horizontally 

 extended, and present the ordinary 3 joints, the last being undi- 

 vided : but the first is sometimes so short and so closely attached 

 to the second, that it may be overlooked, unless the antennas are 

 removed from the head. At the end of the third joint, which is 

 often elongated, there are usually two much more slender joints 

 forming a style or arista, the first of the two joints being very 

 short. Sometimes this first joint disappears. More rarely the 

 arista is placed a little before and above the tip of the third joint 

 (Ocydromia) or disappears entirely (Euthyneura myricce). The 

 thorax is usually compressed, the vertical diameter equalling or 

 exceeding the longitudinal. The transverse suture of the meso- 

 notuin before the wings is widely interrupted in the middle, or is 

 merely commenced at each side. The mesosternum is but little 

 inclined out of the vertical plane, and is covered by the fore coxae. 

 The wings present considerable variation in the veining. In 

 many the cubital vein is forked, as in the series of families pre- 



* Wiedemannia, and a few allied genera, differ most widely from the first type 

 of structure, and approach that of the Dolichopida. 



t The mcntum being short and withdrawn into the oval cavity ; the proboscis 

 has no apparent joint at the base. 



