[Development of infestation with Varroa jacobsoni O. in bee colonies in Tunisia].

The mite Varroa jacobsoni, an ectoparasite of the honey bee, was imported to Tunisia probably in 1976. Afterwards, this parasitosis caused severe losses of colonies for several years. The continued examination of the level of infestation in colonies of a "GTZ" project stated a steady number of mites since 1980. Only in a few colonies, the infestation was above the limit of damage. Though the colonies in North West Tunisia did not receive any treatment since 1986 there was no increase of infestation. In order to investigate the reason for this the mites' ability of reproduction was examined during two following years. The portion of infertile female mites in the worker brood in most of the colonies was with 50% considerably higher than in Europe. In Brazil, the adaptation between host and mite produced similar low reproduction rates. As, however, in Tunisia the portion of infertile females in the drone brood of the individual colonies corresponded to the one in the worker brood climatic conditions are supposed to be responsible.