(12) 



406 C. GORDON HEWITT. 



bottom of the furrows are several papillae, generally four 

 or five to each interpseudotracheal area, of a gustatory 

 nature the gustatory papillae (figs. 1 and 18, gp.). 



The Fulcrum. This chitinous portion of the pharynx 

 (fig. 1, F.) lies on the lower part of the head and in the 

 rostrum. Kraepelin describes it as being shaped like a 

 Spanish stirrup iron. Its structure will be best understood 

 by referring to the figures. It consists of an outer portion, 

 which is U-shaped in section; the basal portion, which is 

 posterior and forms the floor of the pharynx (which Lowne, 

 unfortunately, terms the hypopharynx) is vertical when the 

 proboscis is extended. This basal portion is evenly rounded 

 at both ends, and at the sides of the upper end there is a 

 pair of processes the posterior cornua (fig. 1, pc.) which 

 serve for the attachment of muscles. The sides of the 

 fulcrum are somewhat triangular in shape ; their upper 

 anterior portions are produced to form the anterior cornua 

 (a.c.) ; here the sides bend inwards at right angles, and 

 meet below the epistomium, upon which the fulcrum is 

 hinged. The fulcrum is therefore quadrilateral in section at 

 the upper proximal end, and trilateral at the lower distal end. 

 The basal portion (fig. 2, b.p.) forms the floor of the pharynx ; 

 the roof of the pharynx is formed by another chitinous piece 

 (r.p.) with a median thickened raphe. This roof lies parallel 

 with the basal piece, and is fused with the sides of the 

 fulcrum. On the membranous wall of the pharynx, between 

 the labium-hypopharynx and the fulcrum, a small chitinous 

 sclerite (fig. 1, fc.) is developed, which Lowne terms the 

 hyoid sclerite. It is U-shaped in section, and serves to keep 

 the lumen of the pharynx in this region distended. 



2. The Thorax. 



As in all Diptera the possession of a single pair of wings 

 has resulted in the great development of the mesothorax at 

 the expense of the other thoracic segments, consequently the 

 thorax is chiefly made up of the sclerites composing the 



