﻿29 



CLASSIFKATIOX. 



Among- the characters which Stal ascribes to this family, the 

 short, or very short, apical segment of labium is the most dis- 

 tinctive. Xisia, Sitz'a and Phaconcnra all possess a long apical 

 lal)ial segment ; many of the species of these genera also possess 

 a median facial ocellus and a large wax plate at the end of the 

 female abdomen, characters which belong to the Cixiiiiac; the 

 neuration of their tegmina is also very .different from any Derbid. 

 I'"or these reasons I exclude them from the family Dcrbidac, but, 

 inconsistently, have included them in this Bulletin because sev- 

 eral of our greatest authorities on Homoptera have considered 

 them as Derbids. There is no doubt that Kcnncsia is closely al- 

 lied to these three genera and will also have to be removed from 

 the Dcrbidac, although, according to Distant, it has a minute 

 apical joint to the labium. 



I have used the neuration of the tegmina for dividing the 

 family into groups, and again for redividing the grottps ; it thus 

 becomes necessary to use a more definite nomenclature than is 

 usual with many workers in Homoptera. The terminology of Com- 

 stock and Xeedham has been employed as it is the one that is most 

 generally known. To make sure of the different systems of 

 nerves 1 have followed the develoj^nient of the tracheal system 

 in the tegmina of the nymph of several groups of Homoptera. 

 The contention that without studying the development it is some- 

 times difffcult. or impossible, to decide to which group the vein 

 belongs, is no argument against the use of this system, as the 

 same disaclvantage is attached to any system. When we do 

 know the development of a greater number of forms. I 1)elieve 

 we shall be able to divide the I-'ulgoroidea into better defined and 

 more numerous families. 1 have not used the neuration of the 

 wings, as in so many forms they are so covered with waxy se- 

 cretions that only by taking them off and cleaning tlu-ni can the 

 neuration be seen with any certainty, an oi)eration thai many 

 workers would not ])erform with many of the small, delicate 

 s])ecies. which are at present so rare in collections. Next to 

 the tegmina the head and thorax present the best characters. In 

 many forms there is a well-dcvcl()])ed process below the antenna. 

 the subaiitciiiial f^roccss, either in the form of a deep keel or 

 plate, or a mcjre or less sjjatulate organ. The best characler on 

 the pronotum is the absence or presence of the "shoulder keel"" : 

 this is a large carina, or flange, running from the anterior margin 

 behind the eves to the hind margin, with which it often amalga- 

 mates, forminsj'. together with tlu- lateral e(Ige~~. which are some- 



