8 Transactions of the Society. 



The tracheae spring from chitinous plates on each side of 

 the deep cleft of the paraglossia The taste-hairs on the side 

 of the paraglossre are numerous. The mandibles are imbedded 

 on the ventral side, but are in L. conspicua Mg. separate and 

 laterally placed, while in Chrysopilus auratus F. they are soldered 

 into the mentum in the median line (plate I. figs. 11-14). The 

 flaps of the paraglossse (labella) curl upwards and form a case 

 for the maxilla?, hypopharynx and labrum, and the exposed sides 

 of the paraglossse are far more chitinous than the inner or dorsal ; 

 several of these points are indicated in the figure of the trophi of 

 L. Scolopacea L. (plate iv. fig. 19, 1904). I believe that, as far as 

 is known, the blood-sucking habit is confined to the genus Leptis. 



The Mycetophilicke, Bhyphidye, and the genus Ceratopogon, call 

 for no further remark except that all the species examined show the 

 mandibles imbedded in the under-side of the labium. In JJIomyia 

 fidiginosa Mg. of the Psychodida?, the mandibles show on the ven- 

 tral side of the labium as a strong rod with a bifurcation at its 

 anterior end.* 



* Since going to press, I have, through the kindness of Mr. H. J. Waddington, 

 had an opportunity of examining some preparations of Mochlonyx velutinus Hxxthb. 

 This Culicid has a mouth somewhat like Corethra, and I can clearly make out 

 the pharyngeal pump. It is therefore obvious that the long styliforrn labium of 

 the blood-sucking Culicidse has been directly developed from a short stout labium 

 like that of Mochlonyx. The larvae also approximate to the form found in Culex 

 more closely than do the peculiar larvae of Corethra. 



EXFLANATION OF PLATE IV. 



Fig. 53. — Labium of Coniccra atra Mg. 6 ■ Seen from the ventral side, to show 

 the mentum. 



„ 54. — Trophi of Gymnophora arcuata Mg. Seen from the dorsal side. The 

 armature appears to be the same in both sexes in this genus. 



,, 55. — Hypopharynx of G. arcuata. 



„ 56. — Dissection of the mouth of Oliviera lateralis F. The paraglossia, the 

 rnentum, in fact all the labium, with the containing membrane sup- 

 porting the palpi, have been removed. To show the process at the 

 base of the labrurn and the connection with the submentum, also the 

 degeneration of the pharynx. 



,, 57. — Dissection of the labrum of Myiospila meditabunda F. The stipites 

 bearing remnants of maxillary palpi articulate on to the sides of the 

 labrum, which is highly developed. Compare with fig. 61. 



„ 58. — Trophi of Siphona geniculates Deg. Dorsal view ; to show the Muscid 

 trophi specialised for flower feeding, and the adaptation of the sub- 

 mentum into a sucking organ ('?). The degenerating labrum and weak 

 stipites may also be noted. 



,, 59. — Mentum of Musca corvina F. To show the absence of the median suture. 



,, 60. — Mentum of M. meditabunda. To show the same. 



,, 61. — The hypopharynx and the plate on the dorsal side of the labium in 

 M. meditabunda. The hypopharynx is in a very weak condition com- 

 pared with the labrum. The lateral rods are the imbedded mandibles. 



,, 62.— Trophi of Lispe tentaculata Deg. Lateral view. The dark mass in the 

 paraglossse are the teeth, which are very strong. The hypopharynx is 

 thickened at the base and pierced by the pharynx, but the labrum 

 is also used as a suctorial organ, and communicates with a tube lead- 

 ing through the submentum. 



