1922] Otanes: Head and Mouth-Parts of Mecoptera 317 



of the genus Panorpa the two-toothed condition of the mandibles. 

 Examination of the mandibles of Panorpa americana and Panorpa 

 lugubris shows that they are distinctly three-toothed. The mandibles 

 of Merope are slightly emarginate at the middle of the mesal margin. 

 Those of Boreus are six-toothed, the teeth decreasing in size toward 

 the proximal portion of the mandible. Bittaciis (Figs. 2, 8) has a 

 distinctly different type of mandibles. They are greatly elongated, 

 sword-shaped, and end in a prominent distadentis. There is also a 

 rudimentary mesal tooth. At the meso-proximal portion of each 

 mandible, there is present a conical projection, the function of which 

 is not clear. Hine (1898), in his paper on the genus Bittacus failed 

 to notice this, as may be judged from his descriptions and figures. 

 The mandibles of Apterobittacus (Figs. 6, 16) are very much like those 

 of Bittacus. In all the mandibles of the Mecoptera here considered, 

 there is a prominent swelling on the caudo-proximal portion, a condyle, 

 known as the postartis (ptc) , which articulates in a distinct acetabulum 

 of the postgena, the postcoila (ptl. Figs. 50, 52, 59). Each mandible 

 articulates on its cephalic aspect to the precoila of the clypeus by means 

 of another condyle known as the preartis (py). The tendons, to which 

 the muscles of the head are attached, controlling the movement of the 

 mandibles, are well developed. The lateral tendon, which is the 

 smaller of the two, and to which the extensor muscles are attached, 

 is known as the extensotendon (et), and the mesal tendon, to which 

 the retractor muscles are attached, is called the rectotendon (rt). 



The maxillse are well developed in the Mecoptera. The maxillae 

 of Panorpodes oregonensis (Fig. 49) and P. carolenesis (Fig. 45) are 

 very similar and they represent the most generalized condition of all 

 the species examined. The maxillae of Boreus are the most specialized 

 owing to the fact that they are completely fused with the labium. 

 The cardo (ca) in all the species is undivided and is strongly chitinized. 

 In both species of Panorpodes, the cardo is triangular and with a few 

 prominent setae at ventro-lateral angle. It is also triangular in Panorpa 

 and is provided with a few small setae, whereas it is subquadrate in 

 Bittacus (Fig. 41) and Apterobittacus (Fig. 44) and the setae, as in 

 Panorpodes, are prominent. The two cardines in Merope (Fig. 46) are 

 club-like in outline and there is in each cardo a prominent projection 

 on its ventro-mesal margin. The cardines in Boreus (Fig. 36) are fused 

 and together with a part of the submentum form a somewhat elliptical 

 plate. The stipes (s) is also strongly chitinized, generally club-shaped; 

 in Panorpodes, Bittacus, Apterobittacus and Panorpa and with prom- 

 inent setae. As has been already stated, the maxillae of Boreus are 

 fused with the labiimi so that it is impossible to ascertain the mesal 

 extent of the stipes. The stipes (s) in Merope (Figs. 46, 47) are broad 

 and fused at the proximal end. There are two prominent lobes distad 

 of the stipes in all the species. The outer or lateral lobe has been 

 designated by other workers, among whom are Hine, Miyake and 

 Crampton, as the galea and the inner or mesal lobe as the lacinia. 

 In nearly all the species studied, the so-called lacinia is always the 

 larger and the better developed of the two lobes, which is an anomaly, 



