Porrect. Projecting straight forwards ; applied to antennae or palpi. 

 Post-alar callus. A more or less distinct, rounded swelling situated between 



the root of the wing and the scutellum, often inconspicuous or absent. 

 Posterior legs. The hindermost four taken together, the last pair only being 



termed the hind legs. 

 Postical vein. The 5th longitudinal vein. 

 Prcefurca. The portion of the 2nd longitudinal vein lying between its origin 



and its forking. This is the sense in which Osten Sacken employs the 



term and in which it is used in the present volume, but Verrall uses it 



in the BKACIIYCERA to denote " the common origin of the 2nd and 3rd 



veins," in other words for only that portion of the 2nd vein between its 



origin and the origin of the 3rd vein. 

 Pre-alar callus.- A more or lees distinct, rounded swelling in front of the 



root of the wing, on the side of the mesonotum, just behind the outer 



ends of the transverse suture. 

 Prc-sutural depression. A quite small depression, generally triargular in 



shape, situated at each end of the transverse thoracic suture, close to 



the commencement of the dorsopleural (notopleural) suture. 

 Procephala. Brauer's name for the superfamily containing the MYDAID.E, 



AsiLiD.Eand BOMBYLIID.E ; Bezzi also adopts it. 

 Propygium. Bergroth's name for the hypopygium. 

 Protkorax. The anterior part of the thorax, in Diptera often indistinctly 



marked off from the main middle part or mesonotum. 

 Proximal. Nearer to the body of the insect, the base of a wing or leg, and 



so on ; as opposed to distal, distad. Proxinoad is the corresponding 



adverb. 

 Pseudotrachece. Radiating ridges ou the inner opposable sides of the 



labella in many Diptera, which " serve as a means of attrition, by 



which the insect rubs off particles of food from firm substances " 



(Williston). 



Pteropleura. The pleural area immediately below the root of the wings. 

 Ptilinum.A. small but powerful bladder-like organ, present in the 



CYCLORHIIAPIIA only, situated just above the base of the antennte on the 



frons. It is only used by the insect to escape from the puparium, by 



inflating it, upon which it protucles through the frontal suture and 



springs off the cap of the puparium. 

 Pubescence. The clothing of soft hairs common to nearly all Diptera in 



different degrees, not short or dense enough to be known as pile, nor 



containing bristles. 

 Pulvilli. "Two pad-like fleshy cushions attached to the last joint of the tarsus 



below the claws, usually present, but often absent among the 



ORTHORRHAPIIA, and often much larger and better developed in the <5 



than the 9 " ( Willis(on'). 

 Puncture. A minute indentation of the surface. 



Radical cellA, term" used by a few of the older authors for the basal 



cells. 

 Jt'homboidal cell. A small four-sided cell near the end of the costa in 



TIPUUD.E. At first Osten Sacken called it the trapezoidal cell. 



