High prevalence but relatively low impact of two eucharitid parasitoids attacking the Neotropical ant Ectatomma tuberculatum (Olivier)

Composition and dynamics of ant communities may be influenced by highly specialized, specific parasitoids such as eucharitids. Yet, little is known about their prevalence in ant societies. Through systematic monthly excavation of ant nests, we evaluated the impact on the Neotropical ant Ectatomma tuberculatum of two eucharitid parasitoid species, Dilocantha lachaudii and Isomerala coronata, which simultaneously attack the same host populations in southern Mexico. Nearly 90% of all the nests collected through the year were parasitized, with an average of 13% ant pupae and 6.7% ant larvae parasitized by eucharitids, and an annual loss of 17% of the ant brood. Eucharitid prevalence among host nests was, however, very variable, and only some E. tuberculatum nests were severely weakened (100% of ant brood parasitized). Parasitism was highest during the dry season (January-March), just when the production of ant pupae was minimum: up to 50.6% of the ant pupae were destroyed in March. However, production of E. tuberculatum males and females occurred later (June-July), and the reproductive potential of the host colonies did not ultimately seem to be heavily affected by eucharitid parasitism. Differences in the seasonal timing of eucharitid attack and ant reproduction thus have the potential to modulate the impact of eucharitids on ants. Our results are discussed in the context of the impact of eucharitids upon E. tuberculatum colonies and their possible effect on the community structure of this potential biocontrol agent ant.