Metamorphosing insects often have complex and poorly known life-histories. In particular, what they feed on during their larval stages remains unknown for the vast majority of species and its documentation only results from difficult and time-intensive field observations, rearing or dissections. Through the application of a DNA analysis of gut contents in adult parasitoid wasps, we were able to selectively sequence a diagnostic DNA marker that permitted the identification of the host used by these wasps during their larval stages. By reproducing these results in species with different life-histories, we excluded other potential sources of host DNA, confirming that after ingestion by the parasitoid larva the host DNA can persist through metamorphosis in the abdominal contents of the adult wasp. Our discovery considerably extends the applicability of molecular analysis of gut contents by enabling documentation of the food used by insects during their larval stages and thus increasing the accuracy and precision of food web-studies. The 24% success rate of our approach is surprisingly high considering the challenging context for host DNA preservation, and we discuss the factors possibly affecting this rate. We propose Molecular Analysis of Parasitoid Linkages (MAPL) as a new method to document host-parasitoid associations at a faster pace and with unrivalled precision. Because of the key regulatory role of parasitoid wasps in ecosystems, which makes them the most commonly used biological control agents, MAPL will have immediate applications in both basic and applied biological sciences.

GenBank_Diptera_MLepR1Sequences for MLepR1 primer binding site in 1990 species of Diptera as retrieved from GenBank on Sep.2010 (via BOLD)GenBank_Lepidoptera_MLepR1Sequences for MLepR1 primer binding site in 2711 species of Lepidoptera as retrieved from GenBank on Sep.2010 (via BOLD)GenBank_wasps_MLepR1Sequences for MLepR1 primer binding site in 342 species of parasitoid wasps as retrieved from GenBank on Sep.2010 (via BOLD)List of 297 wasp records for primer testList of the 297 wasp samples used to test for amplification success of primer MLepR1 in parasitoid wasps.WaspCOI_297samples_Fig2Fasta file for COI barcode sequences of the 297 wasp samples used to test for amplification success of primer MLepR1 in parasitoid wasps.Data 29 retrieved host samplesData file for the 29 records of host samples retrieved from molecular analysis of the wasps' abdominal contents.Data 29 wasp samplesData file for the 29 wasp samples for which host DNA was retrieved after molecular analysis of the wasps' abdominal contents.29Host sequences retrieved from gutsFasta file for the 29 host sequences (partial COI barcode) retrieved from molecular analysis of the adult wasps' abdominal contents.26 of 29 wasp sequencesFasta file for COI barcodes obtained in 26 of the 29 wasp samples from which host sequences were also retrieved after molecular analysis of abdominal contents.29host_boldtracefilesElectropherogram / trace files for the host partial COI barcode sequences retrieved from molecular analysis of abdominal contents of wasp samples using primer pair LepF1/MLepR1.