2 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 122 



were drawn, using a camera lucida. The aedeagus, style, and connec- 

 tive were drawn at 150X; the male plate, valve, and pygofer, as well 

 as the posterior margin of the female abdominal sternum VII, at lOOX. 

 A 0.1 mm scale for both magnifications is found in figure 1; all illus- 

 trations were drawn to this scale. The writer has used the terminology 

 of Kramer (1950) for external stmctures, and of Young (1952) for 

 internal. Descriptions and illustrations were made from long series of 

 specimens unless stated otherwise. Geographical or seasonal varia- 

 tions were not found. Individual variations are illustrated. New 

 scientific names, other than patronyms, shoidd be considered arbitrary 

 combinations of letters. A selective bibliography is included. Metcalf 

 (in press) has compiled a complete list of references through 1955. 



The Balcluthini can be separated from the closely related tribe 

 Macrostelini by the appearance of the basal hind tarsomere which is 

 distinctly sulcate basally in the Balcluthini. Both tribes can be sepa- 

 rated from the remainder of the Deltocephalinae by the presence of 

 only two anteapical cells in the forewdng; there are almost always three 

 anteapicals in the foremng of the remainder of the Deltocephalinae. 

 The dorsal width of the head, including the eyes, compared to the 

 width of the pronotum has been used to separate the Balcluthini into 

 two genera by some workers. The author found no other characters 

 correlated with head width and agrees with those workers who feel 

 that this character is not stable enough for generic distinction. 



The median length of the vertex compared to its length next to the 

 eyes and the distance of each ocellus from its adjacent eye are useful, 

 although they vary somewhat within species. Other characters 

 include the width of the anteclj^^eus and its relationship to the genae. 

 Color of the head and of the species in general is quite variable, and its 

 diagnostic value is generally secondary. The oblique brown lines 

 present on each side of the midline of the face in many species, referred 

 to as muscle maculae in an unrelated species of CicadeUidae by Kramer 

 (1950), are of some value and are noted, when present, in the species 

 descriptions. Few characters of the thorax and abdomen are used 

 except those of the genital capsule and genitalia. Hind femoral 

 chaetotaxy used so effectively by Ribaut (1952) as a generic character 

 varies from 2-2-1 to 2-1-1 within Balclutha. The pronotal length 

 in relation to the median length of the vertex is sometimes useful. 



The most important structure used in differentiating species is the 

 aedeagus. The shape of the male pygofer and plates as well as the 

 connective and stjdes is used to supplement the characters found on the 

 aedeagus. The shape of the apex of the connective is particularly 

 useful in separating groups of species. 



Females are usually quite similar to the males but are usually 

 slightly larger. The only female character used in this study is the 



