219] HEAD OF DIPTERA— PETERSON 49 



distal end of the cephalic groove. They are not well-defined structures 

 in all labia. In Chironomus (Fig. 371), they are two small membranous 

 lobes, while in Simulium (Fig. 366), Rhabdophaga (Fig. 367), Bibio 

 (Fig. 364), and Rhyphus (Fig. 374) they have the form of a single 

 median membranous lobe. The glossae of Simulium are of particular 

 interest since they have a great number of minute chitinized thickenings 

 which radiate from the proximal end. So far as known these thicken- 

 ings bear no relation to the psedotracheae of the paraglossae. The 

 glossae of Tabanus (Fig. 391) are united and form a chitinized triden- 

 tate piece with the median tooth the longest. The glossae of Lonchop- 

 tera (Fig. 407) illustrate a form intermediate between a median spine, 

 such as occurs in Psorophora (Fig. 381), Aphiochaeta (Fig. 393), Empis 

 (Fig. 422), and Exoprosopa (Fig. 426), and the U-shaped structure 

 characteristic of the Cyclorrhapha. The glossae of the Calyptratae re- 

 semble in general the glossae of Musca (Fig. 465). In the genera of 

 this group the cephalic ends of the U-shaped piece are free and project 

 cephalad from the point of attachment of the pseudotracheae. The 

 glossae are not well defined in a few genera, Sapromyza (Fig. 410), 

 Chyromya (Fig. 412), and Chloropisca (Fig. 431), for example, and 

 it is impossible to differentiate the glossae from the chitinized groove 

 of the mediproboscis and the proximal ends of the pseudotracheae. The 

 glossae of Promachus (Fig. 379) are specialized in that they give rise 

 to two thickenings which extend dorsad in the groove of the labium 

 and serve as guides for the hypopharynx and galeae. 



EPIPHARYNX AND HYPOPHARYNX 



The anterior end of the alimentary canal of the Orthoptera and 

 of insects in general is divided transversely into two parts, one forming 

 the cuticular lining of the clypeus and labrum and the other the lining 

 of the opposite side of the mouth cavity. The portion lining the clypeus 

 and labrum is known as the epipharynx (ep), and that of the opposite 

 side as the hypopharynx (hp). Each lining may be subdivided into 

 several parts. These are of particular significance in a study of the 

 epipharynx, which has a distinct chitinized mesal piece, and two lateral 

 chitinized pieces which are situated near the clypeo-labral suture. These 

 lateral pieces, which have been designated as tormae (to), and, so far 

 as I know, are described here for the first time, project cephalad toward 

 the clypeo-labral suture in Melanoplus (Fig. 515) and Gryllus (Fig. 

 516) and connect with both the labrum and clypeus. In Gryllus they 

 are interpolated between the clypeus and the labrum and appear as 

 small triangular sclerites on the cephalic aspect. The tormae of Peri- 

 planeta (Fig. 514) are not as well developed as in the above-named 



