Aphid DNA detection by molecular gut content analysis in a natural enemy consuming honeydew

In agroecosystems, understanding of predator–prey interactions are a prerequisite for the use of natural enemies of pest arthropods. Molecular gut content analyses using prey‐specific primers for polymerase chain reaction (PCR) have been widely developed to identify the essential natural enemies of pests. However, these techniques may include uncertainties: interactions other than predation between the studied organisms and pests could result in the detection of the pest DNA in the gut of a supposed predator. Here, we tested whether the DNA of aphids was detectable in their honeydew and in gut content samples of a natural enemy that had consumed honeydew but had never contacted the aphids. We used the cotton aphid, Aphis gossypii (Hemiptera: Aphididae), and larvae of the green lacewing Mallada desjardinsi (Neuroptera: Chrysopidae) that prey on aphids and suck honeydew. By using specific primers for the aphid, we detected that 79.2% of honeydew samples tested positive for the aphid DNA. Aphid DNA was detected in 36.7% of lacewing larvae that had consumed honeydew, in the absence of direct contact between lacewing larvae and aphids. Evaluation of aphid predation by DNA‐based gut content analysis, therefore, carries the risk of determining that an arthropod has preyed on aphids when, in fact, it has not. We believe that PCR results should be interpreted with caution when estimating predation.