56 
Psyche 
[March-June 
A different arrangement is obtained by considering divergence 
from an unspecialized tibia on the basis of posterior spur position 
relative to the tibial apex and to the most proximal point of the 
setal band. The protibia of Opisthius , for example, is little modified, 
yet cleaning setae are present; the antenna cleaners of other cara- 
bids can be derived from this sort of configuration along two parallel 
evolutionary pathways. In the isochaetous pathway, large proximal 
shift of the setal band occurs without shift of the posterior spur; 
while in the anisochaetous pathway, shift of band and spur occur 
together. 
In each pathway, divergence from an unspecialized protibia has 
similar components: 
1 ) Proximal development, elongation and differentiation of the 
setal band into a distal and a proximal cleaning portion. 
2) Origin and development of the medial expansion and the 
cleaning arc. 
3) Shift of the antennal channel from vertical to oblique. 
4) Anterior-posterior compression of the tibia. 
5) Degree of development of anterior and posterior setal rows. 
Based on the degree of development in the above mentioned factors, 
the forms examined can be divided into three grades diagnosed as 
follows : 
Grade A : Setal band short, almost entirely horizontal, located 
close to distal rim of medial face; confluent zone, if present, very 
short; SB/Tb less than 20 per cent. Medial expansion absent. 
Antennal channel long, vertical. Anterior row always present, 
posterior row may not be used in cleaning. Tibia not compressed 
antero-posteriorly. 
Grade B: Setal band long with distinct vertical section and con- 
fluent zone, SB/Tb between 26-58 per cent, but is usually less than 
40 per cent. Confluent zone short, ranging from 15-35 per cent of 
the length of the band. Medial expansion present, except in Miletus , 
but is usually not shifted far anteriorly. Antennal channel shallow 
and developed far above clip setae, or not. Tibia not compressed 
antero-posteriorly. 
Grade C: Setal band, long (SB/Tb 33-69 per cent) divided 
into a large distal region, or confluent zone, and a proximal clean- 
ing arc. Distal region varying from 33-69 per cent the length of the 
setal band. Medial expansion well developed anteriorly. Channel 
deep, short, does not extend above clip setae. Anterior and posterior 
rows, if present, usually do not form cleaning aggregations. 
