THE HEAD CAPSULE. 121 



The Frons exhibits three sclerites, a triangular epifrontal, 

 and two subquadrate frontals (Fig. 23, j, /). The three 

 simple or median eyes are situated near the angles of the 

 epifrontal. On either side of the frontal plates there is a 

 narrow sclerite, the parafrontal ; it is formed in the anterior 

 edge of the paracephalon. 



The Face assumes the form of a semi-elliptical shield ; it is 

 bounded above by the antennal ridge, and below by the epi- 

 stome ; the large third joints of the antertnse almost conceal it. 



Two sclerites are developed in this region— my mesofacials, 

 the fovese of Desvoidy ; these are distinct in the young imago, 

 but become subsequently fused into a single plate (Fig. 24, /, m/). 



The Antennal Ridgfe is a distinct sclerite in the young imago, 

 continuous with the facial edge of the paracephalon ; it presents 

 a median process, which descends between the antennfe, with 

 a deep emargination, on either side. This ridge corresponds 

 with the toruli and the antennal rostrum; it is distinct in 

 the young imago, but becomes fused with the mesofacials 

 in the adult (Fig. 24, /, r). 



The lunula is seen immediately above the antennal ridge. 



The anterior edges of the paracephala overlap the face 

 slightly, and form a setigerous chitinized fold on either side 

 of the face ; these are the facialia of Desvoidy. 



The Epistome (Fig. 23, j, c) is but little developed in the 

 Blow-flies; it consists of a narrow, somewhat salient, ridge, join- 

 ing the facialia below the face. In the Sjrphida; it forms a large 

 beak-like shield, in which several distinct paired sclerites are 

 developed. The epistome in the Cicadae is very similar to that 

 of the Syrphida;. 



The Paracephala exhibit three distinct sclerites in front, the 

 parafrontals, the facialia, and the genai. The latter appear to 

 be the anterior and lower part of the great lateral plates of the 

 head, extending forward beneath the great eyes. Fig. 23, j, 

 exhibits a lateral view of the head of an immature imago ; the 

 folds of the paracephala, from which the parafrontals, the 

 antennal ridge, the facialia and the epistome are subsequently 

 developed, are very distinctly seen. 



