muir: two new species of ascodipteron. 363 



place it with the last three families. In some muscids (i. e. Musca 

 domestica) a small protuberance, with a few hairs attached to it, indi- 

 cates the position of a rudimentary palpifer. 



That the palpi in Diptera are maxillary is easily demonstrated 

 by following them through such families as Asilidae, Bombyliidae, and 

 Syrphidae. 1 In the Schizophora they arise from the oral membrane, 

 owing to the reduction of the maxillae, and have only a slight muscular 

 connection with the stipites; in a few species they are absent and a 

 small sclerite indicates their position. In those genera in which the 

 trophi are abortive the palpi are also absent. 



The maxillary palpi are large in most of the Pupipara, although they 

 have often been described as absent. In Glossina (Plate 3, fig. 21, mp.) 

 they arise from the oral membrane, near the base of the proboscis, 

 the distal two thirds meeting together to form a cover for the distal 

 part of the proboscis. In Hippobosca (Plate 3, fig. 20, mp.). They 

 arise from the oral membrane, near its attachment to the head-capsule 

 and meet together to form a cover for the distal portion of the pro- 

 boscis. In Nycteribiidae, Streblidae and the male Ascodipteron they 

 arise from the oral membrane near the anterior (or dorsal) edge of the 

 oral margin and cannot cover the proboscis (Plate 3, figs. 22, 23, mp.). 

 In the female A. speiserianum the stipites are attached to the base of 

 the labrum, as in the Streblidae; there are no traces of palpi. 



The labrum and labium. Of all the trophi of the female A. speiseria- 

 num it is the labium that has undergone the greatest specialization, 

 and offers the greatest interest. In the Calyptratae the proboscis 

 generally takes the form of a tube, in which the hypopharynx lies, 

 the ventral, and major, part of the tube being formed by the labium, 

 the dorsal part by the labrum-epipharynx. The labium is composed 

 of two large sclerites, the dorsal and ventral plates, joined together by 

 the lateral membranes (Plate 3, figs. 27-32, dp, vp, Im). The dorsal plate 

 is longitudinally grooved on its dorsal surface, or, to describe it more 

 accurately, its lateral edges are curved up dorsally. The ventral plate 

 also has its lateral edges curved up dorsally, sometimes so greatly 

 that they fold round and partly envelop the dorsal plate (Plate 3, figs. 

 28-29, dp. vp.) In Glossina palpalis the proboscis is similar to that 

 of Melophagus but the differentiation of the globular basal and their 

 distal portion is not so marked. 



1 1 cannot follow Mr. Wasche in his arbitary method of calling the palpi maxillary 

 or labial. His "law " does not hold good, as in some cases, where reduction of the 

 maxillary has left the palpi isolated on the oral membrane, they still have a muscu- 

 lar connection with the stipites. 



