12 U.S. NATIONAL MUSEUM BULLETIN 261 



of gross macrosetae, or tliere may be intercalary small macrosetae ar- 

 ranged uniseriately between the gross macrosetae. 



Also, on the hindlegs, the relative length of the first tarsomere com- 

 pared to the combined length of the second and third tarsomeres has 

 been found to be useful in the present study. The length is measured 

 from a lateral or mesal aspect, so that the joints and not merely the 

 tarsal subsegments are seen. 



On the forewing, useful characters include the presence or absence 

 of a membrane and its extent when present, whether or not the veins 

 are elevated, the sculpturing and texture of the surface, the number of 

 cells at the apical margin and their relative length, the presence or 

 absence of supernumerary crossveins, and whether or not the claval 

 veins are fused. Apical cells are numbered beginning at the commissural 

 margin when the wings are at rest. The brachial cell is that cell of the 

 corium which is adjacent to the claval suture. 



On the hindwing, whether vein R2+S is interrupted or not has been 

 found to be of taxonomic importance (fig. Ig). 



The male genitalia provided a number of characters useful in the 

 present classification. Abdominal segment IX, the pygofer, may or may 

 not be strongly produced posteriorly, and the contours of its dorsal and 

 lateral margins are often useful. The chaetotaxy of the surface of the 

 pygofer is also used. Two sorts of setae are found on the pygofer — one 

 notably thicker than the other at low magnifications. The thicker setae 

 are referred to as macrosetae ; the thinner (visually linear at low magni- 

 fications) as microsetae. The distinction is admittedly loose but it 

 works well in practice, for few cases of setae of intermediate thickness 

 (small macrosetae) have been found. The pygofer also frequently bears 

 processes of which the point of origin and the shape have been used as 

 characters. The sternum of the male abdominal segment IX bears a 

 pair of lobes, the plates, in all Cicadellidae. Their length, shape, 

 chaetotaxy, and degree of fusion along the median line are of taxonomic 

 value. 



Also, in the male, a pair of styles form a part of the so-called "internal 

 genitalia." Their length and form are useful although not always 

 consistent intraspecifically. Extending between the basal portions of 

 the styles is the connective, which has been regarded as a basal piece of 

 the intromittent organ by morphologists. Its length and form and the 

 presence or absence of a dorsal median keel are of taxonomic 

 significance. 



In most Cicadellidae, the apical portion (aedeagus) of the intromittent 

 organ articulates basally with the connective. In the Cicadellinae there 

 are numerous exceptions to this, and it is believed that departures from 

 this widespread condition have occurred independently in several 



