An essential component of the insect cellular response is phagocytosis. Analyses of the in vitro phagocytosis could be useful for the studies of the relationship between insects and their pathogens. Fungal metabolites are known to inhibit phagocytosis whereas components of the fungal cell wall stimulate phagocytosis. To achieve a better understanding of fungal pathogenesis in insects, haemocyte populations of two insect species susceptible to Conidiobolus coronatus infection (Galleria mellonella, Dendrolimus pini ) were compared with haemocytes of the resistant species (Calliphora erythrocephala ). Fungal infection increased phagocytic activity of G. mellonella plasmatocytes 3.3 times and this of D. pini plasmatocytes 2.1 times. Analysis of infected C. erythrocephala larvae did not reveal any influence of C. coronatus upon phagocytic activity.