E. Hargreaves :]'27 



appears to be to get rid of the excreta (lioneydew). The lingula moves 

 in a vertical plane, while the operculum moves slightly backwards and 

 forwards. The anus opens on the dorsal surface of the lingula (anterior 

 to it) (Fig. 55). Ventral to the base of the lingula is a cleft, which is 

 presumably to allow the lingula greater freedom of movement. Leading 

 from the base of the lingula near the anus to its tip is a row of rather 

 long setae, and at the tip there is a depression surrounded by them. 

 It would appear that the honeydew is conducted from the anus via the 

 row of setae, to the tip of the lingula, in the depression of which it can 

 accumulate and form a globule. It is got rid of by the flicking of the 

 lingula. This flicking is easily seen in the case of the pupa. The 

 honeydew on exposure becomes gradually more and more viscous, 

 and if it were not for the above arrangement the anus would become 

 occluded, and the insect killed. The position of the anus corresponds 



Fig. 5(5. Vasiform oritice with solidified honeydew. 



with the general up-side-down habit of the insect on the under leaf- 

 surface. In some of my preparations there is a mass of clear structure- 

 less material filling in the space between the lingula and operculum. 

 This is honeydew which had become so viscous that the insect could 

 not get rid of it (Fig. 56). It may be that the fly had remained in an 

 upright position for some time. 



Peal^, 1903, considered that the lingula secreted the honeydew. 



Miss Bernis^ {Proc. U.S. Nat. Mas., vol. xxvii, p. 475) supports 

 Peal. 



Quaintance^ could not find a definite opening at the tip of the lingula, 

 and states that whether the anus opens at the base or tip, the lingula 

 functions as the supra-anal plate. He homologises the lingula with 

 the supra-anal plate of the Psyllidae, where the anus opens at the tip. 



The small numerals refer to the bibliography. 3, 5, U, 7, 8, and 9 are quoted from 

 Quaintanee 1913. 



