62 
Psyche 
[March-June 
of a segment will be groomed, or uneven pressure will be applied. 
In grade A systems, the setal band is horizontal and located close 
to the tibial apex. These facts impose restrictions on grooming 
behavior. The setal band and the flattened surfaces of the apical 
segments can be parallel only if the tibia is placed in a narrow zone 
near the level of the antennal insertion. Outside this zone, dorsal 
movement of the head or posterior rotation of the coxa will draw 
the antenna obliquely through the band. This is especially so since 
the antennal segments (looked at as an ellipse in cross section) are 
capable of little motion parallel to the semi-major axis. The pro- 
tibia of Scaphinotus, and perhaps other grade A forms as well, is 
stationary after reaching the substrate, maintaining the geometric 
relationship between the antennal surface and the band throughout 
a sequence. 
Since the band is located close to the tibial apex, and since the 
spurs contact the substrate during grooming, the antennal segments 
about to be cleaned are dragged across the substrate (Fig. 33). And, 
the antenna, as a whole, undergoes considerable bending, parallel 
to the semi-minor axis. 
In grade C configurations, the cleaning arc is vertical and located 
above the tibial apex. Movement of the tibia will not pull the 
antenna out of alignment with the band since the antenna is gripped 
by the clip setae and is capable of considerable movement parallel 
to the semi-minor axis. While the antenna is drawn through the 
cleaning setae, by movements of both the head and proleg, the apical 
segments do not contact the substrate nor is the antenna bent 
(Figs. 35, 36). 
In permitting use of an additional grooming movement, coxal 
rotation, by developing vertical cleaning elements; and in prevent- 
ing the antenna from contacting the substrate, by moving the 
cleaning seatae proximally, the grade C system is an improvement 
over grade A. The setal band in grade B forms has a vertical 
grooming component that is not developed far above the tibial apex 
(Fig. 13). In these forms, coxal rotation can be a grooming move- 
ment but the antenna may come in contact with the substrate. 
Grade B systems may be intermediate functionally as well as struc- 
turally. And so, the three grades of antenna cleaners, defined above 
on structural criteria, represent grades of improvement in the antenna 
cleaning mechanism. 
There are two types of evidence which suggests that the three 
grades represent sequences of historical development: 
