Pupae were injected with β−1,3-glucans (green dots) – a highly conserved pathogen-associated molecule that acts as an immune elicitor of the invertebrate immune system – or ant physiological saline as a control (grey dots), and tested for their change in immune gene expression 48 hr after injection. Injection with β-glucans did not affect the gene expression of (A) the melanisation cascade-regulating gene proPO (Cerenius and Söderhäll, 2004) (saline: Mann-Whitney U test, U = 69, p=0.06, β-glucans: U = 55, p=0.75) within 48 hr of injection. However, both (B) PGRP-SC2, an IMD pathway regulator gene (Bischoff et al., 2006), and (C) β−1,3-GBP, a pattern recognition protein that specifically binds to fungal β-glucans (Ma and Kanost, 2000; Gottar et al., 2006), showed increased gene expression 48 hr after injection, compared to pupae immediately after injection (PGRP-SC2: U = 17, p=0.0095; β−1,3-GBP: U = 19, p=0.01), but not following saline injection (PGRP-SC2: U = 70, p=0.06; β−1,3-GBP, saline: U = 81, p=0.0095, a significant down regulation). Data points display the difference in gene expression 48 hr after injection to mean gene expression immediately after injection; statistical analysis was carried out on full data set. Solid lines ± shaded boxes show mean ± 95% CI. Asterisks show groups where gene expression (48 hr after injection) differs significantly (p<0.05) from expression immediately after injection (dotted line); *=p<0.05; **=p<0.001; ns = non-significant.