The Mouth-parts of the Nemocera, etc. By W. Wesche. 39 



other genera, Scatopse and Dilophus. From dissection it is seen 

 that the palpi do not adhere to the cardines of the maxillae, and are 

 quite away from them. This is exceedingly difficult to under- 

 stand, because these four-jointed palpi are so much like the palpi 

 in Simulium, Psychoda, Chironomus and Ehyphus, which are un- 

 doubtedly maxillary. However, similar palpi are found in Dilophus, 

 agreeing in all particulars, having the sense-organ in the second 

 joint, and these are undoubtedly labial. Scatopse has single- 

 jointed labial palpi. The mandibles are found adhering to the 

 bases of the paraglossae on the ventral side, and enclosed in the 

 membrane of the labium ; the tracheae have a very modest develop- 

 ment, but the labrum is strong, is hinged on to the cardines of the 

 maxilla?, and the hypopharynx is large, seems to have fused at its 

 base with some portion of the submentum or fulcrum, and is much 

 ciliated. The labium is exceedingly long in Dilophus, short in 

 Bibio, and still shorter in Scatopse. The mouth-parts of these 

 three genera are at first sight unlike, yet they will be found to 

 have characters in common ; in Dilophus they seem specialised 

 for flower-sucking ; and, as in Bibio, though smaller, the vestiges of 

 the mandibles can be seen on the ventral side. Scatopse is so 

 small that it can readily penetrate with its whole body into the 

 nectaries of most flowers ; I have often seen it feeding on the juices 

 of the ivy blossom. Bibio also has a suctorial mouth-part, but the 

 armature on the fore legs, found in both sexes, inclines me to 

 suspect it of occasionally seizing prey (pi. VI. figs. 2-7). 



The mouth-parts of Dolichopus possess one feature which 

 separates them from all other families in Diptera : the tracheae on 

 the paraglossae are of the most curious description. Under high 

 powers, each one of them appears to be made up of a number of 

 sub rectangular, semi-transparent cells, which decrease in size as 

 the tracheae approaches the edge of the labellum ; at its extremity is 

 ii very short blunt hair inserted in a minute cylinder. In Medcr- 

 terits truncorum Mg. it has another appearance, rather granular and 

 less differentiated. In most genera of this family the cardines of 

 the maxilke are very anteriorly placed— the points on which the 

 palpi are usually situated, (close to the base of the labrum,) are 

 quite at the extremity of the paraglossae, and have feathered pro- 

 cesses at the extremities, which are probably the remains of the 

 maxillary palpi. The mentum has a central rod, which ends in a 

 point between the paraglossae ; this rod has a median suture, and 

 is homologous with the paired rods found in Bibio and the ventral 

 •apodeme in Tipula, and represents the mandibles. This character 

 is found in several families, and marks them off from the Muscidao, 

 where the mandibles are on the dorsal side of the labium. The 

 labrum is elaborately toothed and haired, and covers a powerful 

 hypopharynx, with a deep channel, connected with a suctorial 

 trachea, the true pharynx. The palpi are single-jointed, with a few 



