We know almost nothing about the significance of carabid larvae in biological control. This ignorance arises from difficulties in identification and sampling. Identification of adults is challenging enough when closely related species are found at a given locality, but identification of the larvae is especially problematic, because distinguishing morphological features are lacking or difficult to use. Larvae can be correctly identified by using polymerase chain reaction (PCR) primers to amplify their cytochrome oxidase I sequences and matching them to those of correctly identified adults. The sampling problem is less tractable: most investigators have used pitfall trapping, which does not yield absolute density estimates, but rather some index of activity and density that is affected by stage- and species-specific responses to weather and trappability. Also, adults and immatures tend to be found in different strata, the adults being mainly epigeal or foliar while the larvae tend to be found in the litter and soil, sometimes to depths of several centimetres.

Previously unpublished absolute density data and the few published quantitative data show that immature predator densities can be considerable, often rivaling or exceeding those of adults. Greater use of absolute density sampling methods, coupled with PCR-based species identifications and molecular gut analysis, will enable an appreciation of the biocontrol potential of larval carabids.