highly significantp < 0.0001
Fitting a generalized linear model with negative binomial errors to the data on number of thalli per individual from infected nests (fitted dispersion parameter θ = 4.39) showed a highly significant difference between nests in the level of infection (Wald χ 2 = 245.05, df = 1, p < 0.0001), and also a strong effect of estimated worker age (Wald χ 2 = 70.3, df = 4, p < 0.0001), with older workers having a higher load of thalli (Fig. 7 ), but no association with the presence or absence of P. alcon caterpillars (Wald χ 2 = 0.719, df = 1, p = 0.396).