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Reticulitermes flavipes workers were topically inoculated with approximately 10,000 conidia of the entomopathogenic fungus Metarhizium anisopliae. After being kept in groups of 20 individuals for 1-9 d, histopathological examination showed that termites had an individual immune reaction. The nodule formation at the point of entrance of the fungal hyphae was identified as a cellular encapsulation and the different steps in the nodule formation are described. The relative number of hemocytes per termite increased 24h after fungal exposure and remained high in the hemolymph for at least 3 d before decreasing back to pre-exposure levels. The role of an individual immune cellular reaction in social insects is discussed.

Reticulitermes flavipes workers were individually inoculated with 10,000conidia of the entomopathogenic fungus Metarhizium anisopliae. After being kept in groups of 20 individuals for 1-6d, histopathological approach showed that most of the inoculated conidia were groomed from the surface of the cuticle by nestmates within 24h, and that a large number of conidia was subsequently found in different parts of the gut of the groomers. Our observations showed that, among thousands of conidia found in the termite's gut, conidial germination never occurred in all inspected specimens, even when the conidia had the chance to bind to the surface of the cuticular lining of the gut. In addition, when termites were left for decomposition several days after death caused by an external infection of M. anisopliae, the hyphal growth was generalized in the body cavity of the cadaver, but was never observed in the lumen of the gut even 2d post-mortem. Our observation suggests that the putative biochemicals involved in the termite's gut defense against fungal pathogens are from multiple origins.

Antifungal activity of norharmane, a beta-carboline alkaloid found in termites (Isoptera, Rhinotermitidae) was tested against two entomopathogenic fungi, Metarhizium anisopliae and Aspergillus nomius. It was determined that, at physiological concentration (10 microg ml(-1)), norharmane had no significant effect on A. nomius mycelial growth rate but reduced M. anisopliae growth rate by 11.9%. Contrary to previous findings, we suggest that norharmane has a limited role in disease resistance against fungal pathogens in individual subterranean termites, and we discuss the potential role of this chemical at a colony level.