1988] 
Buschinger et al. — Chalepoxenus brunneus 
261 
parasitic queen by adult host workers, however, occurs in all Epi- 
myrma species, not only in the degenerate slave-makers. This 
acceptance in Epimyrma thus is a preadaptive feature already 
present in the slave-making species; it is certainly favorable for a 
degenerate slave-maker who, when workerless, cannot replenish its 
slave stock through raiding. In Chalepoxenus brunneus, on the 
contrary, the queens had to evolve de novo the capability of being 
accepted by adult host workers. 
It remains an open question of whether or not C. brunneus is on 
the way to an even more specialized type of coexistence with the 
host queens, a true inquilinism. Some of our experiments seemingly 
support such an assumption. However, the observed instances of 
coexistence between the C.b, and the host queens might well be 
artifacts due to inappropriate laboratory conditions. In the field 
such a coexistence has not been observed. And also in C. muelleria- 
nus and C. kutteri , in a total of now close to 500 field colonies 
checked, a coexistence of host and parasite queens has never been 
found. In laboratory colony founding experiments, however, it has 
been recorded in a couple of instances, also in these species 
(Ehrhardt unpubl.). 
As was demonstrated in our laboratory cultures of C. brunneus, 
the production of sexuals is markedly queen-biased, with a numeri- 
cal sex-ratio close to 0.43 (male/ female). This might indicate a cer- 
tain degree of inbreeding, with sexuals mating close to the maternal 
nests; in fact we saw mating behavior within our narrow formica- 
ries. The apparent absence of a female sexual pheromone would fit to 
this assumption. Queen bias is usually found in such parasitic (and 
also free-living) species, where inbreeding occurs, most evidently in 
Epimyrma species with mating inside their nests (Buschinger and 
Winter 1985, Douwes et al. 1988). For a discussion of this feature 
see Buschinger (in press). 
The C. brunneus population of Tizi-n’-Test, according to our 
observations, is very small, covering an area of not more than 50 X 
100 m, and is certainly isolated. The species has not been found in 
close vicinity nor in farther distant sites of similar elevation, exposi- 
tion, etc., despite our spending several days in search of additional 
localities. With an estimated population of less then 100 nests at any 
time a high degree of inbreeding is inevitable, even if sexuals do not 
mate exclusively with those of the same, or closely neighboring, 
nests. 
