1957] 
' Adenuga — Ants and Homoptera 
27 
However, one aspect of this mutualistic association, which is inci- 
dental but nevertheless significant for the host plant carrying the ants 
and the Homoptera, is the capacity of some of the Homoptera to 
transmit fungal and viral diseases to the host plant. 
Laboratory tests have confirmed that all the mealybugs have been 
found to transmit strains of virus diseases (Thresh et al., 1959) but 
Planococcoides njalensis is now considered the most important vector, 
especially of the virulent types of swollen shoot virus (Leston, 1970). 
Workers of Crematogaster spp. and Macromischoides have been ob- 
served actively carrying up cocoa trees particles of soil which they 
use in building their nests. During the rainy season this sort of 
activity will no doubt help to spread fungal spores of the black pod 
disease ( Phytophthora palminlvora ) . 
There is therefore some contrast in the roles played by ants in the 
entomological problems of cocoa crops. Predaceous ants like Oeco- 
phyllaj Crematogaster and Macromischoides more or less determine 
the composition of the insect spectrum. An extensive survey of cocoa 
farms in Nigeria for these three also confirms Leston’s (1970) work 
in Ghana that each cocoa farm carries a mosaic of these dominant 
species in which the three species are more or less mutually exclusive 
(see Tables below) . 
These tables show that the coincidence of Oecophylla and Macro- 
mischoides (Table ib) is occasional, that of Oecophylla and Cre- 
matogaster (Table 1 a) very rare and that of Macromischoides and 
Crematogaster (Table ic) extremely rare. Leston (1970) claimed 
that up to fifty percent of Ghana’s cocoa trees are permanently pro- 
tected by Oecophylla from Distantiella (mirid) damage in some 
areas. There is little doubt that both Macromischoides and Cre- 
matogaster are negatively correlated with mirid ( Distantiella and 
Salbergella) population densities (Adenuga, unpublished report). 
On the other side of the scale is the fact that these ants increase the 
damage to cocoa crops because they encourage the establishment of 
viral and fungal homopterous vectors by actively transporting them 
and to a limited extent offering them protection against their natural 
parasites and predators. In addition, Macromischoides does direct 
damage, although minor, to cocoa leaves by stripping them to build 
its nest. 
A decision as to whether or not to encourage the establishment of 
these ants in cocoa farms will depend on whether mirid infestation 
is more or less important than fungal and viral diseases of cocoa in 
a particular locality. 
