WILLISTON: APIOCERID^. 



113 



MYDAID^. 



In Mydas, and probably in all those species with but two posterior 

 cells between the forked cell and the posterior margin of the wing, the 

 mouth-parts are relatively small, the proboscis short, and the palpi 

 extremely rudimentary. On the other hand, in the three known gen- 

 era with three posterior cells behind the forked cell, Diochlistus, 

 Triclonus {Hamnophand) and Mitrodetus, the proboscis is more or 

 less elongate, and, in one form at least, has well-developed palpi. In 

 Mydas, there is a slight, wart-like protuberance from the basal plate, 

 which probably represents the palpus. From its base, the short, 



m /• 



Mouth-parts of Triclonus bispinifer Westw. 



a, paraglossEB, from below; b, ligula, from above; c, palpifer; d, palpus; 



e, galea; f, labellum. 



•dagger-shaped palpifer arises. The united paraglossae is longer than 

 the ligula, and nearly twice the length of the palpifers. It is slender, 

 nearly cylindrical, nearly truncate at the tip, and has its lower borders 

 nearly contiguous. The slender, obtuse ligula fits within this tube, 

 and itself forms nearly a complete tube. The short galea terminates 

 in broad labella. 



In Triclonus, the palpi are elongate and well developed, though 

 unjointed. The paraglossae and ligula are slender, the palpifers only 

 a little longer than the palpi, the galea more elongate, and freely 

 open above; and the pseudo-tracheate labella very large and turned 

 downward. 



