| Čoahkkáigeassu: | The natural resistance of heartwood from thirteen forest species (six of Tropical Rain Forest and seven of Pine-Oak Forest) to subterranean termites Heterotermes sp. attack, was evaluated by field microtests. Small blocks (2.5 × 2.5 × 5 cm) of each species were settled in 4 racks made of a highly susceptible wood, following a latin square arrangement. The racks were placed on the soil of the test area, in a tropical deciduous forest of the Biological Station "La Mancha", Veracruz, México. The total exposure period was 15 months. Natural resistance was evaluated by means of termite damage, according to a visual-rating system with five categories. Tropical rain forest woods were more resistant that pine-oak forest woods. For certain species, differences in the rank of attack were found between raks, possible causes of this variability are discussed. The classification of woods was: Highly Resistant: Guarea chichon, Swietenia macrophylla (Meliaceae); Quararibea funebris (Bombacaceae). Resistant: Pinus patula var. longepedunculata (Pinaceae); Lysiloma acapulcensis (Leguminosae).Moderately Resistant: Pinus patula, Pinus aff. pseudostrobus (Pinaceae); Quercus acatenangensis (Fagaceae). Susceptible: None. Highly Susceptible: Quercus crassifolia (Fagaceae); Alnus jorullensis (Betulaceae). In the case of Pinus teocote (Pinaceae); Schizolobium parahibum (Leguminosae) and Licania platypus (Rosaceae) no conclusive results were obtained.
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