We examined the ability of M. croceipes to learn, detect, and respond to 2,4-DNT, which is a volatile discriminator of trinitrotoluene (TNT). The percentage of conditioned wasps to detect and respond to the various concentrations of 2,4-DNT for >= 15 sec was measured. Significantly more of the conditioned wasps responded to the concentration of 2,4-DNT used for conditioning than other concentrations examined. Accordingly, percent conditioned wasps to respond >= 15 sec could be used as a suitable measure to screen air samples and distinguish between samples with or without the target odorant. The data recorded in this study indicate the measured behavior could be used to estimate the concentration of target odorants. Data in this study indicate M. croceipes can detect and respond to this compound, which provide further support for its development as a biological sensor. Microplitis croceipes (Braconidae) Animals and man; Sensory reception; Behaviour; Abiotic factors Microplitis croceipes; Animals as tools; Chemoreception; Behaviour; Chemical factors; Detection & responses; forensic significance; 2,4-dinitrotoluene none