308 ME. J. DAVIDSON ON THE MOUTH-PARTS AND 



I should like to take this opportunity of expressing my sincere thanks to 

 Professor Maxwell Lefroy for the many suggestions and advice he has kindly 

 given me during the progress of the work, and also to Mr. Clifford Dobell 

 for much valuable assistance in connection with methods of technique and 

 references to literature. 



II. Technique and Methods. 



Specimens were fixed in Carnoy's fluid and kept in 90 per cent, alcohol. 

 Bouin's picro-formal mixture was also used. 



The mode of preparation of material for the parafiin bath was as follows. 

 After passing through the alcohols to absolute alcohol^ the material was 

 placed in chloroform for several hours, then in a mixture of equal parts of 

 chloroform and wax and finally in the paraffin bath. Paratfin-wax melting 

 at 58° C. was used and the best results were obtained when the material 

 was left in the bath for about two hours. Only the head was imbedded, but 

 for entire specimens a longer time in the bath is advisable. Sections were 

 cut from 4-10 yu, thick, in three planes, transverse, vertical, and longitudinal. 



Normal saline solution, glycerine, and turpineol have been used as 

 examination media. 



For exann'nation of cleared specimens the material was taken through 

 alcohol and cleared in cedar-wood oil, clove-oil, or turpineol, and mounted 

 in alcoholic or xylol balsam. 



Sections were stained with hsematoxylin (Ehrlich) and orange G or eosin. 



For examination of the chitinous parts the material was treated with 

 10 per cent, potash for several hours and then washed in slightly acidulated 

 distilled water and examined in pure glycerine, or mounted permanently in 

 the usual way in Canada balsam. 



The drawings were made from Camera lucida sketches, and owing to the 

 minute detail of the parts very high magnifications were necessary, so that 

 most of the work was done with a -j^ oil-immersion lens, and in the case of 

 figs. 4-14 and fig. 24 a No. 18 occulo was used. 



III. Nomenclature ; Review of Literature. 



The terms used throughout this paper are based solely upon the study of 

 the anatomy, and do not necessarily imply a definite homology with other 

 Hemiptera. It is not intended to discuss in any detail the homologies and 

 morphology of the different parts. As far as possible established names have 

 been given, but generally speaking the terms are mainly used for convenience 

 of description. 



Most of the published work dealing with the mouth-parts of Hemiptera is 

 confined to the division Heteroptera. The deflexed position of the head in 



