May, 191G] Homopteroiis Studies. Part II 301 



insects, a shallow dissecting pan made by filling a watch glass 

 with paraffin, proved very convenient. The study of many of 

 the chitinized parts was facilitated by previously boiling the 

 specimens in a 10 per cent, solution of potassium hydroxide, 

 washing in water and examining in glycerine or alcohol. The 

 former proved very suitable, and has the advantage in that it 

 evaporates very slowly. In the dissection of the reproductive 

 organs and the digestive apparatus, normal salt solution was 

 used to float out the organs. Some of the immature forms 

 were conveniently studied by simply killing in Xylol and mount- 

 ing in balsam almost immediately. Certain structures, such 

 as the tracheal system, show up clearly when treated by this 

 method. 



Material for sectioning was killed mainly by two methods. 

 Hot water was used where the insect has recently moulted 

 and the chitin had not yet hardened. Carnoy A (Glacial 

 acetic acid one part, to absolute alcohol three parts) proved 

 to be a very good fixing fluid. Practically all the material 

 for sectioning was killed by this method. Delafields haema- 

 toxylin and eosin were the stains used for staining sectioned 

 material. Staining in toto did not prove satisfactory. Picric 

 acid for staining chitin was used to some extent. The material 

 was embedded and cut in paraffin with a melting point of bh C. 



THE HEAD. 



External Anatomy. (PL XXI, XXII, Figs. 1, 2, 3, 4, 5, 7, 25-31). 

 The different regions of the Jassoid head have been well 

 defined by systematists in the group and before proceeding 

 to a discussion of the structure, it will be as well to outline 

 these regions, which now, for the most part, are of interest 

 because of their place in the taxonomy of the superfamily. 

 The dorsal region, i. e., the portion of the head between the 

 compound eyes is termed the vertex (v), and in some of the 

 families it bears the paired ocelli (o). Although not a definite 

 sclerite, it serves as a good "landmark" for descriptive purposes. 

 The region from the anterior edge of the vertex to the first 

 apparent transverse "suture" is regarded as the front ("frons") ; 

 its lateral margins are limited by the longitudinal sutures which 

 run from the antero-lateral edges almost to the antennae and 

 frequently to the anterior edge of the head. Attached to the 



