Biological active compounds used by worker bees to repel ants

Abstract

The use of resin or propolis forms an important part of the social bees’s nest defense systems. Cracks and other small openings are sealed by propolis in the hive of the European honey bees, Apis mellifera, to prevent intruders. The dwarf honey bee, Apis florea, and the small dwarf honey bee, Apis andreniformis, build sticky resin rings around the branch at each side of the nest. The stingless bees apply this resin to the inner surface of the entrance tube to prevent invasion ants. There are substantive number of publications indicating that bees use propolis in defense against diseases cause agent as it has antibiotic, antifungal and antiviral properties. However, its effectiveness as a class of ant repellent is questionable, and has not been reported yet. This study showed that the introduction of the Asian weaver ant. Oecophylla smaragdina, on the comb of A. florea induces a specific behavioral response of the worker bees. After worker ant exposure at the top of the comb, the number of worker bees on the sticky band zone increased significantly and remained at higher level for 2 hours. Additionally, more sticky material was deposited by the bees after ant exposure. This behavior was not observed after exposure of am empty forceps, a Tenebrio molitor larva or an another arboreal predatory ant, Crematogaster rogenhoferi. A biotest was developed to compare the reaction of the Asian weaver ants, O. smaragdina and of the European red wood ant, Formica polyctena to the repellent compounds of resin material from various spcial bee species (three species from the genus Apis, six species from the genus Trigona). Tests were performed in two different geographic regions, in Southeast Asia (Thailand, Malaysia) and in Europe (Germany). In the tropical region, the repellent efficacy of the Asian bee material on Asian weaver ants was significantly stronger than that observed on the European red wood ant, F. polyctena, and visa versa. That is, the material from nest of the European honey bee, A. mellifera showed a higher repellent effect upon the European red wood ant, than did the material; from the nests of the Asian bees. Pentane extracts of the resin were found to contain ant repellent compounds and these were further analyzed by partial purification using column chromatography. Fractions from column chromatography was assayed in the above biotest for ant repellent activity. Positive fractions for this activity were then characterized by GC-MS. Their mass spectra were taken and compared with an existant spectrum library. As a result, for chemical groups were identified: terpenoids, long chained hydrocarbons, phenol derivatives and naphthalene derivatives. Moreover, about seven compounds which were found in significant quantities in the positive fractions could not be identified by comparison to the spectra contained within the reference library.