MECHANISM OF SUCTION IN SCHIZONEUKA LANIGEKA. 309 



the Homoptera gives rise to several structural differences between the two 

 divisions. 



The description throughout refers to the head in the feeding position, so 

 that the clypeal or dorsal face of the fore-head is spoken of as the anterior 

 or dorsal face, and the surface which is adpressed to the venter in repose, as 

 the posterior or ventral face*. The distal end of the fore-head is towards the 

 extremity of the labrum and the proximal end towards the epicranial 

 region of the head. 



Several of the earlier anatomists, for instance Westwood and Burmeister, 

 tried to homologise the mouth-parts of sucking insects with those of the 

 mandibulate or biting insects, and in 1853 Gerstfeld published a paper 

 dealing specially with the mouth-parts of sucking insects. Geise (1883) 

 published a paper on the mouth-parts of Notonecta, Nepa, and Corixa, and 

 described the salivary pump (Wanzenspritze) which Mayer had described in 

 Pyrrliocoris apterus in 1874. Wedde (1885) dealt with the mouth-parts of 

 some Rhynchota and made some observations on the method of suction. Two 

 years later Leon (1887) studied Pentatoma, and made observations on the 

 homologies of the parts. The next important paper is that of Heymons 

 (1899), who made many interesting additions to our knowledge of the 

 morphology of the Hemipterous trophi. The most valuable contribution 

 within the last few years is that of Bugnion and Popoff (1911). These 

 authors have dealt specially with Graphosoma lineatum, but have also studied 

 several other species of Heteroptera. In an introductory chapter they give 

 many of the different views held by previous workers, as to the homology of 

 the different parts of the trophi. 



!So far as the Homoptera are concerned very little work has been done. 

 Smith (1892) attempted to homologise the mouth-parts of Cicada with those 

 of Diptera, but his work was much criticised by Marlatt (1895). In 1898 

 Smith published a further paper upholding his views that the proboscis and 

 stylets are maxillary structures, and that no trace of mandibular structures 

 occur in any present form of Hemiptera. 



Meek (1913) published an important work on the mouth-parts of Cicada 

 septendecim, in which he shows the close relationship existing between the 

 structure of the head and trophi in this Homopterous insect and the many 

 Heteropterous insects that have been studied. He also gave an account of 

 the method of suction. During the past two or three years Muir and 

 Kershaw have made some interesting additions to our knowledge of the 

 morphology of the mouth-parts in Heteroptera and Homoptera. Their 

 conclusions are based chiefly on the study of the development of the embryo 

 of Pristhesancus papicensis and of Siphanta. They have also made a general 

 comparative study of different families, and have endeavoured to show 



* Vide footnote on p. 311. 



27* 



