340 
Psyche 
[Vol. 92 
dirty ants that freeze when disturbed. The entire dorsal surface is 
covered with soil-binding pilosity that enhances accumulation of 
dirt particles (Holldobler and Wilson, 1986). In Z. varians and Z. 
setulifer, the complex setae and the accumulation of dirt is also 
restricted to the exposed surface, in this case the cephalic disk. Here 
too, camouflage is enhanced by lack of motion, since guards remain 
stationary at the entrance. 
Pilosity 
The structure of setae on the cephalic disc differed among the four 
forms of Zacryptocerus we examined ( varians , pallens, pallens por- 
rasi, and setulifer). Z. varians and the typical form of Z. pallens bore 
setae typical of the genus: a flattened blade arched over a shallow 
pit. Setae of this form probably do not encourage accumulation of 
extraneous material on the disc surface. 
Both Z. pallens porrasi and Z. setulifer, however, had upright 
brush setae that probably do enhance collection of material. The 
setae on Z. pallens porrasi were thick and split to the base, much 
like a shaving-brush. They appeared identical to hairs found in the 
genus Eurhopalothrix. More slender brush hairs split only near the 
tip are common throughout the Basicerotini (Holldobler and 
Wilson, 1986). Both forms of brush hairs are correlated with soil- 
binding in these cryptic terrestrial ants. 
In Z. varians, Z. pallens and Z. pallens porrasi, all hairs on the 
cephalic disc were of a single type. In Z. setulifer, there may be more 
than one hair type on the head, if the hair pattern is similar to that 
found on the thorax. One type was the erect brush hair and the other 
was an appressed blade-like holding seta. This double-layered 
arrangement is common in ants that bind soil particles to their 
cuticle (Holldobler and Wilson, 1986). 
Kempf (1958), in his revision of the Cephalotini, struggled with 
variability of pilosity and disc sculpture within the pallens complex. 
In the end, he lumped all forms into one species. In view of our 
findings, some of the confusing variation in sculpture and pilosity 
may be only apparent and due to varying degrees of coverage, rather 
than actual structural differences. The value of pilosity as a taxo- 
nomic tool may deserve re-evaluation and could be used to distin- 
guish closely related species in what appears to be a pallens 
complex. 
