In most cases, juvenile spiders observed to be hosting wasp larvae were collected live in the field and taken to the lab for rearing (Figs 1, 5, 9). The adult wasp was allowed to fully develop, killing the host spider in the process. In one record from France, the wasp had already killed its host and pupated inside a loose silk cocoon (Figs 18, 19). In all cases, the host spider died as a subadult and the body was left in poor condition, rendering positive identification by means of traditional morphology unreliable (Figs 2, 3, 6, 10, 11, 14, 17). DNA extractions were performed using the Thermo Labsystems KingFisher extraction robot at the Naturalis Biodiversity Center DNA barcoding facility. For host spiders, DNA was extracted by placing the entire specimen directly (without grinding) in lysis buffer with proteinase K for the three hour incubation step. After incubation, the specimen was returned to ethanol and the extraction continued using the lysis buffer solution. This caused negligible further damage to the specimen. In one case, DNA was also extracted from a wasp larval exuvium by this method (Fig. 7). For adult wasps, one leg was removed as source tissue for DNA extraction. To obtain the standard animal DNA barcode fragment of the mitochondrial cytochrome oxidase I gene (Hebert et al. 2003), PCR was performed using either the primers LCO1490 (5'-GGTCAACAAATCATCATAAAGATATTGG-3') (Folmer et al. 1994) and Chelicerate Reverse 2 (5'-GGATGGCCAAAAAATCAAAATAAATG-3') (Barrett and Hebert 2005) (for spiders and larval exuvium) or a coctail of primers LCO1490 (Hebert et al. 2003) and LepF (5'-ATTCAACCAATCATAAAGATATTGG-3') paired with HCO2198 (5'-TAAACTTCAGGGTGACCAAAAAATCA-3') (Folmer et al. 1994) and LepR1 (5'-TGATTTTTTGGACATCCAGAAGTTTA-3') (Hebert et al. 2003) (for adult wasps). PCR reactions contained 18.75µl mQ, 2.5µ 10x PCR buffer CL, 1.0µl 25mM of each primer, 0.5µl 2.5mM dNTPs and 0.25µl 5U Qiagen Taq. PCR was performed using initial denaturation of 180s at 94°C, followed by 40 cycles of 15s at 94°C, 30s at 50°C and 40s at 72°C, finished with a final extension of 300s at 72°C and pause at 12°C. Sequencing was performed by Macrogen (http://www.macrogen.com). For all barcoded specimens, sequences, images, and collection data were uploaded to the Parasitoid Wasps and Spider Hosts project (PWSH) on the Barcode of Life Database (BOLD; http://www.boldsystems.org/). The "Species Level Barcode Records" search of the BOLD database assisted in host spider identification. Where that was unsuccessful, we resorted to the "All Barcode Records on BOLD" search option and Blast search on NCBI's Genbank (http://www.ncbi.nlm.nih.gov/sites/gquery). Historical literature records of host-parasitoid associations relied on the World Ichneumonoidea database (Yu et al. 2012); primary literature was typically not consulted. For Dutch specimens, latitude and longitude coordinates are converted from the local RD (Rijksdriehoeksmeting) coordinate system; for the French record, coordinates are latitude and longitude. All voucher specimens are deposited in the collection of the Naturalis Biodiversity Center with the exception of one wasp retained in the personal collection of Kees Zwakhals (KZPC).

Figure 18.  

Zatypota anomala (RMNH.INS.593866) undergoing metamorphosis in the field.

Figure 19.  

Silk coccoon of Zatypota anomala (RMNH.INS.593866) in the field.

DNA barcoding is best thought of as a supplement, not a replacement, for traditional methods of taxonomic identification because both approaches have different, often complementary strengths and limitations (Dayrat 2005, Will et al. 2005). There are now many examples where the integration of DNA sequence data and morphological data have advanced knowledge in ways that would not have been possible without this synergy (Riedel et al. 2013, Paquin and Hedin 2004). The study presented here is a case where morphology alone is not adequate because of the physical condition and developmental stage of the host at the time of death. Fortunately, we found that the condition of the host specimens did not prevent the generation of DNA barcode sequence data.

Major advances in the study of host-parasitoid relationships require primary data from a wide taxonomic and geographic range. Questions about host specificity and changes in host-parasitoid relationships across large spatial scales are two important topics hamstrung by the scarcity of primary data. But the slow pace of traditional approaches means that few specialists can be dedicated to this area of study. These days, DNA barcoding requires far less expertise, opening the door for more non-specialists to contribute data in small quantities. Depositing these data online in community databases like BOLD, and publishing results in an internet savvy journal dedicated to aggregating datasets of all sizes, offers a strategy for advancing knowledge of host-parasitoid relationships not available to previous generations of scientists.