486 



NORTH AMERICAN DIPTERA 



reduced to slight swellings in some apterous forms. They are supposed 

 to be the rudiments of the second pair of wings but I doubt this. The 

 removal of the halteres renders the insects unable to fly. 



Holoptic — Eyes contiguous, dividing the front into an upper and lower part. 



Humeral crossvein — A crossvein situated near the base of the wing and ex- 

 tending from the costa to the auxiliary or subcostal vein and continuing 

 to the first vein. 



Humeri — The anterior corners of the mesonotum usually more or less well 

 marked. 



Hyaline — Transparent. 



Hypopleura — The space below the posterior spiracle and above the posterior 

 cox?e. 



Hypopleural bristles — Bristles on the hypopleura, usually in a vertical row. 



Hypopygium — The male genitalia together with the adjacent parts. It is 

 composed of several of the apical abdominal segments and is variously 

 modified. 



Infra-squamal setulae — Fine hairs below the point of attachment of the 

 squamae. 



Intercalary vein — A term sometimes applied to the posterior branch of the 

 fourth vein in cases where its base partly closes the discal cell (M2). 



Interfrontal (bristles or hairs) — Hairs or bristles on the frontal vitta. 



Interfrontalia — The frontal vitta. 



Intra-alar bristles — Bristles situated behind the suture and between the supra- 

 alar and dorsocentral bristles. 



Jowls — The cheeks, behind the depressed anterior part. Sometimes termed the 

 peristoma. 



LabellEe — The lips of the proboscis. Supposed to be the modified labial palpi. 

 Sometimes broadly expanded, at other times much reduced or apparently 

 lacking. 



Lamella (e) — A leaf-like plate. 



Lamellate — Broadened and flat: leaf -like; bearing lamellae. 



Large crossvein — The crossvein closing the discal cell; posterior crossvein (ni 

 and M3). 



Lateral — At, toward, or pertaining to the sides of the body. 



Lunula — A term applied to the more or less crescentric area above the an- 

 tennai in some flies, notably in the Syrphidaj. Also a lunulate marking. 



Lunule — See lunula. 



MOUTHPARTS OF FEMALE TABANUS. 



lb, labium; m, mandible; mp, maxillary palpus; mx, maxilla. 



