1985] 
Wheeler & Holldobler — Cryptic phragmosis 
341 
Encrusting material 
The accumulation of material on heads of soldiers and queens 
was common to all the species we examined. In some cases the 
accumulation was extreme (Fig. 8b, 10a) and in some it was slight 
(Figs, la, 3b). Remarkably, the material seemed to be internal in 
origin, rather than an accretion of environmental debris. The glan- 
dular origin of the material was suggested by the following aspects 
of external morphology, but confirmation awaits histological study. 
First, thousands of pores resembling glandular openings covered the 
head of the Z. varians soldier, as shown in Figs, lb, 3b. Second, 
material caught in the process of extrusion was found in Z. pallens 
(Fig. 6). The diameter of the fibers in both Z. varians and Z. pallens 
was appropriate for the size of the pores. Finally, examination with 
a light microscope of the material on Z. varians did not suggest a 
fungal origin. The possibility that some of the material found in the 
dense mats of fibers were fungal mycelia (Fig. 8a) has not been 
completely eliminated, however. 
The fibrous material may not be the only type of material 
extruded onto the disc surface. A sheet of material covering the 
floor of the disk was seen on some specimens of Z. varians (Fig. 3b). 
In addition, what appeared to be a blanket of thicker material 
coated the floor of the apparently clean specimen of Z. pallens 
porrasi (Fig. 7b). The even coating may not be confined to the queen 
and soldier castes. Minor workers of Z. varians appeared to be 
coated with a homogenous layer of coagulated film over the surface 
of the head. 
The function of the fibrous material on the cephalic discs of sol- 
diers and queens is not entirely clear. When the whole bowl of the 
cephalic disc is filled with material, as in Z. pallens porrasi and Z. 
setulifer , a camouflage role seems likely. In less extreme cases, the 
possibility of crypsis is less obvious. However, a thin, grimy layer 
may be sufficient visual or tactile camouflage in some environments. 
The internal origin of the material on the cephalic discs contrasts 
with the extraneous origin found in the Basicerotini and Stegomyr- 
micini (Holldobler and Wilson, 1986). It may be that in the arboreal 
environment in which all cephalotines live, suitable dirt particles are 
relatively scarce, and a more reliable source of camouflage material 
is from within. In Z. pallens porrasi, Z. setulifer, and the Basicero- 
tini, complex setae enhance the accumulation of material, regardless 
of its source. 
