14 BRITISH CICAD.E. 



the ventral salivary glands, noted by Burmeister.* 

 Amongst the Aphides these silky flocks are insoluble 

 in alcohol, and have a composition somewhat analogous 

 to silk. But the products from the large foreign 

 Cixiidae and Flatida3 are distinctly of a crystalline 

 waxy nature ; and such a material forms one of the 

 varieties of the Chinese wax of commerce known as 

 pcla. 



The general characters of the Cixiidae are as 

 follow : — 



Ocelli two or three, and placed on the frons, half- 

 way from the apex. First joint of the hind tarsi with 

 no spur at the base. Nervures much divided in the 

 elytra, and often studded with setigerous bulbs or 

 granules. Body wide and depressed. Head small, 

 and, taken with the eyes, distinctly narrower than the 

 pronotum. Ocelli placed on the sides of the head, 

 with the indication of a third near to the apex of the 

 facial keel. Elytra and wings ample, hyaline, and 

 rounded at the apices. First joint of the hind tarsi 

 elongated. 



The British genera are divided by Stal and 

 Sahlberg into insects furnished with five keels on the 

 scutellum (Oliarus), and insects with three keels 

 thereon {Cixius). 



Although the British species are few, they are not 

 easy to separate with sharpness one from the other ; 

 hence the somewhat doubtful character of their 

 diagnosis, and their involved synonymy. An adequate 

 study of foreign forms will greatly help to decide 

 between specific and merely sporadic varieties. These 

 last often materially differ amongst themselves in 

 markings and colour from the normal forms. 



Mr. Edwards has lately made an attempt to tabulate 

 the "essential characters" of our English species. 

 His scheme is based in great measure on the size, 



* Also " Observations on Coccidae, No. 3," by Mr. Albert C. Morgan, 

 Ent. Mo. Mag., January, 1889, p. U9. 



