A. O. Adenuga.
Mutualistic Association between Ants and Some Homoptera—Its Significance in Cocoa Production.
Psyche 82:24-28, 1975.

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MUTUALISTIC ASSOCIATION
BETWEEN ANTS AN;D SOME HOMOPTERA
- ITS SIGNIFICANCE IN COCOA PRODUCTION*
Department of Plant Science,
University of Ife, Ile-Ife (Nigeria)
During my field collections of ants in some cocoa farms on Ondo Road in Western Nigeria, I have come to observe that certain species of ants are associated with scale insects (Coccidae), mealybugs (Pseu- dococcidae) and aphids in a way which suggests that the .association must be mutually beneficial. Although a great deal has been done by many workers to determine experimentally the nature of this asso- ciation (Strickland, 1951; Nixon, 1951 ; Way 1954), there seems to be so much variation in the degree of the ant-Homoptera association that many questions still remain unanswered. Further, many claims by previous workers need to be substantiated, particularly as these claims in some instances are contradictory. In this paper I present an account of the ants and Homoptera that were observed in asso- ciation on the cocoa farm in West Nigeria, an analysis of this associa- tion, and a discussion of the effects of the association on the cocoa crops. Although there are records of ant-Homoptera association for Ghana and some other parts of West Africa (Strickland, 1951 ;
Leston, 1970) these are the first such records, as far as I am aware, for Nigeria.
The following is a list of Homoptera attended to varying degrees by ants :
Family Pseudococcidae
Planoooccoides sp. nr. njalensis ( ?)
Phenacoccus hargreavesi (Laing)
Planococc,us citri (Risso)
Ferrlsia virgata (Cockerell)
Dysmicoccus brevis (Cockerell)
Family Coccidae
Gascardia sp.
*Manuscript received by the editor February 20, 1975 Psit-fn. Μφ2:24-2 (1975). hup Wpsycht einclub org/82/82-024 html



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19571
Adenuga - Ants and Homoptera
Family Margarididae
Icerya purchasi (immature stages)
Family Diaspididae
Aspidiotus destructor (Signoret)
A onidiella replicata ( Lindinger)
Family Aphidae
Toxoptera aurantii (Boyer de Fonscolombe) (alate and apterous, all immature stages)
Family FIatidae ( ?)
Genera and species undetermined (all immature states) The following genera of ants were found associated with mealy- bugs ( Family Pseudococcidae) listed above : Subfamily Myrmicinae
Crematogaster spp. - workers only
(subgenus Sphuerocrema) C. striatula, C. luctans, C. lek, C. boxi.
(subgenus) Crematogaster group.
(subgenus) A topogyne group - Crematogaster af ricana. 'Pheidole spp. (megacephalu being the most notorious). -
Macromisch~oides, Atopomyrmex, Cataulacus, Monomorium, Meranoplus, Xiphomyrmex, Tetramorium and Solenopsis. Subfamily Forrnicinae
Oecophylla, Acantholepsis, Polyrachis and Camponotus. Subfamily Ponerinae
Platy thyrea
The mealy bugs found in association with ants can be divided into two groups - those for which the association is obligatory and those for which it is facultative. Ptanococcoides njalensis, alone in the first group, is regularly attended by ants. The obligate nature of this association is not surprising; since the mealybugs have very short legs and are ovoviparous, they most probably depend on the ants for transportation from tree to tree. The other mealybugs on the above list are facultative and are only sometimes 'found with ants. They have longer legs and all are oviparous.
Gascardia sp. (Coccidae) is regularly attended by Oecophylla longinoda, Crematogaster africana and Macromischoides acuteata. On the other hand, the association of Icerya purchasi (Margarididae), Aspidiotus destructor and Aonidiella replicata (Diaspididae) with
the same ants is facultative.




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Psyche
[March
Table la.
Oecophylla and Crematogaster (Cr.) Interaction Oecophylla
Present Absent Total Ratio
Cr. Present
6 211 217 1:35
Cr. Absent 243 1010
1253 1 :4
Chi-squared (X2) = 36.3 significant at P < 0.001 Table lb.
Macromischoides (Macr.) and Oecophylla Interaction Oecophylla
Present Absent Total Ratio
Macr. Present 9 105
114 1 :12
Macr. Absent
240 1125 1365 1 :4.5
Chi-squared (X2) = 14.55 significant at P < 0.001 Table 1c.
Crematogaster (Cr.) and Macromischoides Interaction Cr. Present
Cr. Absent
Macromischoides
Present Absent Total Ratio
Chi-squared (X2) = 96 significant at P < 0.001 There are five forms exhibited by ant-Hornoptera 'mutualism' and these have been exhaus,tively discussed in a review 'by Way (1963). 'Mutualism' is defined as "an association between ants and other in- sects which is mutually beneficial without necessarily implying obli- gate dependence or interdependence" (Way, I 963 ) . These forms include: (i) adaptation of the Hornoptera related to the association with ants; (ii) benefits derived by the Homoptera; (iii) benefits derived by the ants in form of contribution of the Homoptera to the food of the ants; (iv) specificity in the ant-Hornoptera association; (v) ant-Hornoptera association in relation to their natural control.



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19571 Adenuga - Ants and Homoptera 27
However, one aspect of this mu tualis tic association, which is inci- dental but nevertheless significant for the host plant ca,rrying 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 d, 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 olf the black pod disease (Phytophthora palminivora) .
There is therefore some contrast in the roles played by ants in the entomological problems of cocoa crops. Predaceous ants like Oeco- phylZa, 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 ( I 970) 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 la) 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 Macromischwdes and Cre- matogaster are negatively correlated with mirid (Distantiella and Satbergella) 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.




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Psyche [March
LESTON, D.
1970.
Entomology of the cocoa farm. Ann. Rev. Entomol. 15: 273-294. NIXON, G. E. J.
1951. The association of ants with aphids and coccids. Commonwealth Inst. Entomol., London. 36 pp.
STRICKLAND, A. H.
1950. The entomology of swollen shoot of cacao, I: the insect species, involved with notes on their biology. Bull. Entomol. Res. 41: 725-748.
1951. The entomology of the swollen shoot of cacao, 11: the bionomics and ecology of the species involved. Bull. Entomol. Res. 42: 65-103.
THRESH, J. M. AND T. W. TINSLEY.
1959. The viruses of cacao. Tech. Bull. W. African Res. Inst.: 1-32. WAY, M. J.
1954 Studies on the association of the ant, Oecophylla longinodu (Latr.) with the scale insect Saissetia sanzibarensis Williams. Bull. Entomol. Res. 45: 113-134.
1963. Mutualism between ants and honeydew producing Homoptera. Ann. Rev. Entomol. 8: 307-344.




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