We built plant-leaf miner-parasitoid food webs in 19 remnants of a fragmented Chaco forest in central Argentina. We constructed food webs on each remnant from different locations at the forest interior and edges. For each food web, we registered the abundance of species, the species richness of each trophic level, estimated the connectivity of their networks, and the average food chain length. We used structural equation models to evaluate the direct and indirect effects of habitat area and edge/interior location on food chain length mediated by species richness, abundance, and connectivity. 

Leaf miner larvae feed inside leaves, leaving tunnels (mines) easily detectable on the leaf surface. In each site, all detected mined leaves were collected along 50 x 2 m and up to 2 m high transects in November-December 2001–2002 and February-March 2002–2003, within the peak period of insect activity. At each visit to each site, two transects were established in fragment edges (within 5m from the border, N-NE oriented) and three in the interior (at least 10m from the border) summing up 10 transects per site. Due to logistic reasons, two sites received more (15 and 11) and two sites less (9) than ten transects, summing a total of 193 transects. At the end of the 2003 growing season, plants were surveyed independently of the food web, registering species abundance as the percent cover in two 500 m² plots per site, one located at the edge of the forest and one in the interior, overlapped with the area sampled for the construction of the food web.